Phosphor-centric control of color of light

ABSTRACT

Lighting devices and/or systems offer dynamic control or tuning of color of light. The lighting systems utilize sources, such as solid state sources, to individually pump a number of different phosphors of types having relatively high degrees of color purity. The phosphor emissions, however, are still broader than the traditionally monochromatic color emissions of LEDs. The different phosphors can be independently excited to controllable levels, by individually controlled sources rated for emission of energy of the same spectrum. Adjustment of intensities of electromagnetic energy emitted by the sources independently adjusts levels of excitations of the phosphors selected to emit different colors of relatively high purity and thus the contributions of pure colors to the combined light output, for example, to enables color adjustment of the light output over a wide range of different selectable colors encompassing much of the gamut of visible light.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/304,560 Filed Feb. 15, 2010 entitled “Dynamic Control of ColorCharacteristics of Light Using Solid State Source and Phosphors,” thedisclosure of which also is entirely incorporated herein by reference.

TECHNICAL FIELD

The present subject matter relates to dynamically controlling or tuningcolor of light, for example, light produced by lighting systemsincluding fixtures and lamps that utilize solid state sources toindependently pump phosphors that provide substantially pure individualcolors, so that the device enables adjustment of color of a combinedlight output, for example over a wide range of different selectablecolors encompassing much of the gamut of visible light.

BACKGROUND

Recent years have seen a rapid expansion in the performance of solidstate lighting emitters such as light emitting devices (LEDs); and withimproved performance, there has been an attendant expansion in thevariety of applications for such light sources. For example, rapidimprovements in semiconductors and related manufacturing technologiesare driving a trend in the lighting industry toward the use of lightemitting diodes (LEDs) or other solid state light sources to producelight for general lighting applications to meet the need for moreefficient lighting technologies and to address ever increasing costs ofenergy along with concerns about global warming due to consumption offossil fuels to generate energy. LED solutions also are moreenvironmentally friendly than competing technologies, such as compactfluorescent lamps, for replacements for traditional incandescent lamps.

Many solid state lighting systems have offered dynamic color control,however, the adjustment or tuning of the color of the output light hasrelied on LED centric approaches. Many solid state light sources producelight of specific limited spectral characteristics. To obtain light of adifferent color one approach uses solid sources that produce light oftwo or more different colors or wavelengths and one or more opticalprocessing elements to combine or mix the light of the variouswavelengths to produce the desired characteristic in the output light.One technique involves mixing or combining individual light from LEDs ofthree or more different wavelengths (spectral colors such as “primary”colors), for example from Red (R), Green (G) and Blue (B) LEDs. Byselecting the relative intensities of the different sources, for examplethe amounts of red, green and blue light from the sources added to formthe combined output light, it is possible to selectively produce lightcolors over a fairly substantial range of the visible spectrum.

With a LED-centric approach such as LED based RGB, the individual coloramounts can be adjusted easily. However, using almost monochromaticcolors from LEDs as the sources imposes limitations on overallperformance. For example, with the approach using LEDs of threedifferent very monochromatic colors, the output spectrum tends to have asmall number of narrow spikes. For white light settings, this produces alow color rendering index (CRI) or otherwise inferior illumination ofobjects of certain colors where there is a gap in the output spectrum.Even for non-white settings, it may be difficult to produce an actualcolor output that really matches the desired spectral content because ofthe narrow spectrums combined to form the output, so that objects maytake on unexpected hues when illuminated by such light outputs. It ispossible to improve the light quality by providing additional LEDs ofdifferent colors, but that approach increases complexity and overallsystem cost and may still not achieve a desired high quality of lightover a sufficient portion of the intended operating gamut.

There also have been a variety of proposals to enhance solid state lightperformance by adding appropriate phosphors to effectively shift some orall of the energy from the solid state source to a more desirable regionof the spectrum. Although many such techniques are intended to providewhite lighting, some have involved control, for example, to achieve andmaintain a desired color characteristic of the white output light. Forexample, phosphor based techniques for generating white light from LEDs,currently favored by LED manufacturers, include UV or Blue LED pumpedphosphors. In addition to traditional phosphors, semiconductornanophosphors have been used more recently. The phosphor materials maybe provided as part of the LED package (on or in close proximity to theactual semiconductor chip), or the phosphor materials may be providedremotely (e.g. on or in association with a macro optical processingelement such as a diffuser or reflector outside the LED package).However, the tuning of the color or color temperature of the phosphorbased approaches has still relied on dynamic control of different colorLED sources. The phosphor emissions may be somewhat broader than thoseof the LEDs, and for example, might appear pastel or even substantiallywhite. The controlled LEDs used for tuning may be specific color LEDs ofone or more colors selected to adjust the light color characteristic oflight produced by pumping of the phosphor. Like the LED-centric tuningof the substantially monochromatic LEDs, the LED centric tuning of thephosphor emissions may have some narrow spiking in the emissionspectrum, and as a result, the range and quality of light color maystill be less than desirable.

Solid state lighting technologies have advanced considerably in recentyears, and such advances have encompassed any number of actual LED basedproducts, however there is still room for further improvement in thecontext of lighting products. For example, it may be desirable for thesolid state lighting device to provide a tunable color light output ofcolor, however, there is still room for improvements in the range and/orquality of the tunable color light output. Relativelyacceptable/pleasing form factors similar to those of well acceptedlighting products also may be desirable, while maintaining advantages ofsolid state lighting, such as relatively high dependability, long lifeand efficient electrical drive of the solid state light emitters.

SUMMARY

The detailed description and drawings disclose a number of examples thatimplement a phosphor-centric approach to color control that utilizesseparately controllable sources with a particular emission spectrum toindependently pump different phosphors emitting substantially pureindividual colors. This phosphor-centric color control, in several ofthe examples, enables adjustment of color of a combined light outputover a wide range of different selectable colors encompassing much ofthe gamut of visible light. The examples using solid state type sourcesmay also address one, some or all of the needs for improvements and/orprovide some or all of the commercially desirable characteristicsoutlined above.

By way of an example, a disclosed variable color lighting device mightinclude independently controllable sources that are all configured toemit electromagnetic energy in the same predetermined spectrum and anumber of optical elements each arranged to receive electromagneticenergy from at least a respective one of the sources coupled thereto. Adifferent phosphor is disposed in each of the optical elements, forexcitation by electromagnetic energy from a respective one of thesources. Each of the phosphors has an absorption spectrum that includesthe predetermined spectrum of the electromagnetic energy from thesources, and when excited, each of the phosphors has a differentrespective color emission spectrum that is at least substantially pure.The optical elements are arranged so that each phosphor in a respectiveone of the optical elements receives little or no excitation due toelectromagnetic energy from any of the sources coupled to a differentone of the optical elements. A visible light output of the lightingdevice includes a combination of different color lights from thedifferent phosphors, from the optical elements. The color of the visiblelight output of the device is adjustable in response to adjustment ofrespective intensities of the electromagnetic energy of thepredetermined spectrum emitted by the solid state sources to adjustrelative levels of excitations of the different phosphors.

In the disclosed examples, the sources are solid state sources, such asLEDs or the like. Various exemplary phosphors are disclosed, includingsemiconductor nanophosphors such as quantum dots and doped typesemiconductor nanophosphors. In several of the specific examplesdiscussed in the detailed description, each of solid state sourcescomprises one or more light emitting diodes, each light emitting diodeis rated for producing electromagnetic energy of a wavelength in therange of 460 nm and below, and the absorption spectrum of each phosphorhas an upper limit at approximately 460 nm or below.

Several different examples of optical elements are disclosed, as well,such as light guides or containers. Also, the light guide or containerof an element may contain or encapsulate a material bearing therespective phosphor. Solid, liquid and gaseous examples of the phosphorbearing materials are discussed. Phosphors and materials may be chosenso that each material with a phosphor dispersed therein may appearcolor-neutral, e.g. clear or translucent, when there is no excitation ofthe phosphor by a source.

Examples of the lighting devices may include two, there, four or moreoptical elements with respective different phosphors and associatedindependently controllable sources of the pumping energy. In particular,examples with three or four element/phosphors are discussed in which theadjustment of the levels of excitations of the various phosphors enablesadjustment of color of the combined light output over a wide range ofdifferent selectable colors encompassing much of the gamut of visiblelight.

By way on another example, a solid state lighting device for variablecolor lighting might include first and second solid state sources eachconfigured to emit electromagnetic energy in the same predeterminedspectrum as well as first and second optical elements. The first opticalelement is arranged to receive electromagnetic energy from the firstsolid state source. The second optical element is arranged to receiveelectromagnetic energy from the second solid state source but to receivelittle or no electromagnetic energy from the first solid state source.The first optical element is arranged to receive little or noelectromagnetic energy from the second solid state source. The devicealso includes at least two different phosphors. The first phosphor is inthe first optical element at a location for excitation by theelectromagnetic energy received from the first solid state source. Thesecond phosphor in the second optical element at a location forexcitation by the electromagnetic energy received from the second solidstate source. The first phosphor is of a type excitable byelectromagnetic energy of the predetermined spectrum, and when excited,for emitting visible light of a first color that is at leastsubstantially pure. The second phosphor is of a type excitable byelectromagnetic energy of the predetermined spectrum, and when excited,for emitting visible light of a second color that is at leastsubstantially pure. The second color is different from the first color.When the phosphors are excited, a visible light output of the lightingdevice includes a combination of first and second color lights emittedby the first and second phosphors, from the first and second opticalelements. The color of the visible light output of the lighting deviceis adjustable in response to adjustment of respective intensities of theelectromagnetic energy emitted by the first and second solid statesources to adjust relative levels of excitations of the first and secondphosphors.

Any of the exemplary lighting devices as outlined above may by used in alighting system that combines the solid state lighting device with acontroller coupled to the sources, where the controller is configured toimplement independent control of the various sources. Some exemplarydevices take the form of light fixtures, whereas other examples take theform of lamps.

By way of an example, a solid state lighting system for variable colorlighting might include a number of independently controllable sources,where each of the sources comprises one or more solid state devices foremitting electromagnetic energy in the same predetermined spectrum.Optical elements are arranged to receive electromagnetic energy from atleast a respective one of the solid state sources coupled thereto. Adifferent phosphor is disposed in each of the optical elements forexcitation by electromagnetic energy from a respective one of thesources but remote from semiconductors of the solid state devices. Eachof the phosphors has an absorption spectrum that includes thepredetermined spectrum of the electromagnetic energy from the sources.Each of the phosphors emits a different respective color of visiblelight that is at least substantially pure, when the phosphor is excited.The optical elements are arranged so that each phosphor in a respectiveone of the optical elements receives little or no excitation due toelectromagnetic energy from any of the sources coupled to a differentone of the optical elements. When the sources are on, a visible lightoutput of the lighting system includes a combination of color lightsfrom the different phosphors, from the optical elements. The system alsoincludes a controller coupled to independently control the solid statesources, which enables adjustment of respective intensities of theelectromagnetic energy of the predetermined spectrum emitted by thesolid state sources. Such a system enables adjustment relative levels ofexcitations of the different phosphors to control the color of thevisible light output of the lighting system.

Variable color lighting devices and lighting systems using such devicesas disclosed herein and in the accompanying drawings may realize one ormore of the following advantages, particularly in the context of generallighting applications: broader spectrum output at any selected outputcolor setting which produces a higher quality of light than LED-centrictechnologies which tend to have narrow spikes in the emission spectrumat any given color, a wider range of selectable output colors, highefficiency, long service life, and options for a form factor similar toany of a variety of common well accepted products such as those ofincandescent lamps, florescent lamps or neon lamps.

Additional advantages and novel features will be set forth in part inthe description which follows, and in part will become apparent to thoseskilled in the art upon examination of the following and theaccompanying drawings or may be learned by production or operation ofthe examples. The advantages of the present teachings may be realizedand attained by practice or use of various aspects of the methodologies,instrumentalities and combinations set forth in the detailed examplesdiscussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict one or more implementations in accord withthe present teachings, by way of example only, not by way of limitation.In the figures, like reference numerals refer to the same or similarelements.

FIG. 1A is a cross-sectional view of a phosphor-centric tunable colorlight emitting device, with certain elements thereof shown incross-section.

FIGS. 1B-1D are cross-sectional views of the tunable color lightemitting device in FIG. 1A containing two, three and four light guides,respectively.

FIG. 2 is a simplified cross-sectional view of a light-emitting diode(LED) type solid state source, which may be used as the source in atunable color solid state lighting device.

FIG. 3 is cross-sectional view of one light guide/container included inthe tunable color light emitting device of FIG. 1A.

FIGS. 4A, 4B and 4C show certain data, the different phosphor emissionsspectra and the vertices of the operating gamut within the CIE colorchart for the visible light gamut, for a first simulation of four typesof phosphor color emissions of first examples of color purity.

FIGS. 5A, 5B and 5C show certain data, the different phosphor emissionsspectra and the vertices of the operating gamut within the CIE colorchart for the visible light gamut, for a second simulation of four typesof phosphor color emissions of second examples of color purity (purerthan the first examples).

FIGS. 6A, 6B and 6C show certain data, the different phosphor emissionsspectra and the vertices of the operating gamut within the CIE colorchart for the visible light gamut, for a third simulation of four typesof phosphor color emissions of third examples of color purity (purerthan the first and second examples).

FIG. 7A depicts measured spectra of emissions from three exemplaryphosphors, in this case, for red (R), green (G) and blue (B) emissions.

FIG. 7B shows the vertices of the operating gamut within the CIE colorchart for the visible light gamut, for the RGB phosphors in the exampleof FIG. 7A.

FIG. 8 illustrates another example of a tunable color light emittingdevice, with certain elements thereof shown in cross-section.

FIG. 9 is yet another example of a tunable color light emitting device,with certain elements thereof shown in cross-section, combined with acontrol circuit to form an overall light emitting system.

FIG. 10 a cross-sectional view of a tunable color light emitting system,in the form of a lamp for lighting applications, which uses a solidstate source and semiconductor nanophosphors pumped by energy from thesource to produce tunable color light.

FIG. 11 is a plan view of the LEDs and reflector of the lamp of FIG. 10.

FIG. 12 is a functional block type circuit diagram, of an implementationof the system control circuit and LED array for a tunable color lightemitting system.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant teachings. However, it should be apparent to those skilledin the art that the present teachings may be practiced without suchdetails. In other instances, well known methods, procedures, components,and/or circuitry have been described at a relatively high-level, withoutdetail, in order to avoid unnecessarily obscuring aspects of the presentteachings.

The various technologies disclosed herein relate to variable colorlighting devices and lighting systems using such devices. The examplesoffer tunable color control of light output of the devices or systems.The examples implement a phosphor-centric approach to color control thatutilizes separately controllable sources with a particular emissionspectrum to pump different phosphors emitting substantially pureindividual colors. The phosphor-centric color control, at least inseveral of the examples, enables adjustment of color of a combined lightoutput over a wide range of different selectable colors encompassingmuch of the gamut of visible light. The various phosphor-centricdevices/systems may be or may be used in common lighting fixtures andlamps such as those for general lighting applications. Examples ofgeneral lighting applications include downlighting, task lighting, “wallwash” lighting, emergency egress lighting, as well as illumination of anobject or person in a region or area intended to be occupied by one ormore people.

In the specific examples shown in the drawings, the sources are solidstate type sources, such as LEDs, although other sources of energy ofthe appropriate spectral characteristics for the phosphor pumping may beused. Although other types of solid state light emitters may be used,the illustrated examples use one or more LEDs to supply the energy toexcite the phosphors. The solid state type source in such cases may bethe collection of the LEDs. Alternatively, each LED may be considered aseparate solid state source. Stated another way, a source may includeone or more actual emitters.

In the examples, the sources are configured to emit light or otherelectromagnetic energy of the same spectrum, in that they are rated forthe same spectral output, e.g. rated for the same main wavelengthoutput, although in actual lighting devices there may be some variationfrom source to source for example within manufacturer's tolerances.

The sources and respective optical elements containing the differentphosphors are arranged so that each source supplies electromagneticenergy to excite the phosphor in the respective optical element butsupplies little or no electromagnetic energy to excite the phosphor inany other optical element. Stated another way, an optical elementreceives energy from an associated source to excite the phosphor in thatelement, but little or no energy from a source associated with any ofthe other optical elements. In actual practice, there may be someleakage or cross-talk of the pumping energy from one source over fromone associated optical element to another optical element. However, thesources and optical elements are arranged to keep any such cross-talk ofpotential pumping energy sufficiently low as to enable a level ofindependent control of the phosphor excitations to allow the degree oflight tuning necessary for a particular tunable lighting application.For a tunable color lighting application, for example, the opticalseparation needs only to be sufficient to provide control of color inthe output of the desired range of different selectable colors, that isto say, so as to achieve the desired range of system color adjustment.

With that instruction, reference now is made in detail to the examplesillustrated in the accompanying drawings and discussed below. The firstexample represents a lamp product, specifically, a tube lamp, althoughfixture examples are discussed later. Reference now is made in detail tothe examples illustrated in the accompanying drawings and discussedbelow.

FIG. 1A illustrates a first example of a tunable color light emittingdevice 10. As discussed more later, electronic circuitry is combinedwith the device 10, to control the sources and thus control or tune theoutput. The combination of the light emitting device with theappropriate electronics forms a light emitting system. The device and/orthe system may be configured for any lighting application where it isdesirable to vary or adjust a color of the visible output light. Forexample, with the appropriate phosphors, control of the device mightcause it to output a wide range of different colors, encompassing muchof the gamut of visible light. Because of the color purity of phosphoremissions, the lamp may offer at least some color output hues of a highsaturation comparable for example to neon lights. However, the device 10has the capacity for adjustment of the color to output, to provideselectable white light as well as other color hues of high saturation.

Hence, such a system can selectively output light of a particular huewith relatively high color saturation. However, some settings will alsoresult in a relatively white light output. Some white light settings maycorrespond to color temperature points along the black body curve (on orwithin some tolerance range of a point on that curve). Althoughsometimes referred to herein simply as white light for convenience,light produced by excitation of the phosphors in the device 10 may beconsidered “at least substantially” white when the device is tuned sothat the output light would appear as visible white light to a humanobserver, although it may not be truly white in the electromagneticsense in that it may exhibit some spikes or peaks and/or valleys or gapsacross the relevant portion of the visible spectrum and/or may differfrom a black body spectrum for white light.

The variable color light emitting device 10 includes a number of opticalelements 12 comprising containers formed of an optically transmissivematerial and containing a material bearing a phosphor. The variouselements are not drawn to scale but instead are sized in the drawings ina manner to facilitate review and understanding by the reader. As willbecome apparent from later discussion of this first example, eachoptical element forms an optical guide with respect to energy from oneor more sources 11 but allows diffuse emission of light produced byemissions of the phosphor excited by the energy from the respectivesource.

The exemplary tunable color lighting device 10 includes respectivesources 11 coupled to or otherwise associated the various opticalelements 12 to supply pumping energy to excite the phosphors in therespective optical elements. The sources 11 are configured to emit lightor other electromagnetic energy of the same spectrum, in that they arerated for the same spectral output, e.g. rated for the same mainwavelength output, although in actual lighting devices there may be somevariation from source to source for example within manufacturer'stolerances. At least a portion of the emission spectrum for the sources11 falls within all of the absorption or excitation spectra of thephosphors 18 contained in the various light guides 12. Stated anotherway, the absorption or excitation spectra of the various phosphors willhave at least some overlap, and at least a portion of the sourceemission spectrum such as the rated main wavelength of the emissionspectrum for the sources 11 falls within that absorption spectraoverlap.

As discussed more below, the absorption spectra of the exemplaryphosphors in the materials 18 encompass UV and near UV portions of theelectromagnetic spectrum. Those skilled in the art will be aware ofother light sources that fall within the range of such absorptionspectra, such as black light florescent lamps and UV florescent lamps.The examples utilize solid state devices as the sources. Solid statedevices with appropriate emissions spectra are readily available andrelatively easy to independently control.

The sources 11 and respective optical elements 12 containing thedifferent phosphors 18 are arranged so that each source 11 supplieselectromagnetic energy to excite the phosphor 18 in the respectiveoptical element 12 but supplies little or no electromagnetic energy toexcite the phosphor 18 in any other optical element 12. Stated anotherway, an optical element 18 receives energy from an associated source 11to excite the phosphor in that element 12, but little or no energy froma source 11 associated with any of the other optical elements 12. Inactual practice, there may be some leakage or cross-talk of the pumpingenergy from one source 11 over from one associated optical element 12 toanother optical element 12. However, the sources 11 and optical elements12 are arranged to keep any such cross-talk of potential pumping energysufficiently low as to enable a level of independent control of thephosphor excitations to allow the degree of light tuning necessary for aparticular tunable color lighting application of the device 10. For atunable color lighting application, for example, the optical separationneeds only to be sufficient to provide control of color in the output ofthe desired range of different selectable colors, that is to say, so asto achieve the desired range of color adjustment.

The exemplary tunable color light emitting device 10 of FIG. 1 thereforeincludes a solid state source 11 positioned at each end of each of aplurality of light guides 12. Two light guides 12 are illustrated inFIGS. 1A and 1B, three light guides are illustrated in FIG. 1C, and fourlight guides are illustrated in FIG. 1D. FIGS. 1B-1D are cross sectionsof the tunable white light emitting device 10 along line A-A but forvariants thereof containing two, three and four light guides 12,respectively. The light guides 12 are housed within an outer container16 in this example with end caps 14 and metal prongs 14 a for insertioninto a compatible light socket. The outer container 16 is similar to aflorescent tube and may present a similar outer tubular form factor. Thecircuitry (not shown) used to drive the solid state sources 11 may becontained within the caps 14, although if the tube device 10 isconfigured for a fixture similar to that for a florescent lamp, then thecircuitry would likely be contained in a separate ballast like housing.An example of suitable circuitry is described in further detail withrespect to FIG. 12.

The example assumes a straight tube implementation, with thelongitudinal main central section or “tubular portion” of each lightguide 12 and the outer container 16 having cylindrical internal andexternal surfaces. Those skilled in the art will recognize, however,that other tubular shapes may be used, for the light guides and/or thecontainer. The lateral cross-section, for example, could be oblong,rectangular, square or triangular, etc., instead of circular as shown inFIGS. 1B-1D. Also, the tubular light guides and outer container may becurved or bent along their lengths, for example, for some neon lampreplacement applications. Furthermore, the inner and outer surfaces ofany tube may converge or diverge somewhat, either laterally orlongitudinally.

The lighting device 10 utilizes solid state sources 11, rated foremitting electromagnetic energy of a first emission spectrum, in theexamples, at a wavelength in the range of 460 nm and below (λ≦460 nm).The solid state sources 11 in FIGS. 1A-1D can include near ultraviolet(UV) solid state sources, containing a semiconductor chip for producingnear UV electromagnetic energy in a range of 380-420 nm. A semiconductorchip produces electromagnetic energy in the appropriate wavelengthrange, e.g. at 405 nm which is in the near ultraviolet (UV) range of380-420 nm. Phosphors are remotely positioned in the light guide typecontainers 12 so as to be excited by this energy from the solid statesources 11. The phosphors are of types or configurations such that theyare excited by energy in a range that includes the emission spectrum ofthe sources 11, and such that the phosphors together produce light inthe output of the device 10 of a selected color within the gamutencompassed by the points represented by the pure color outputs of theparticular number phosphors used in the device, where the output coloris selected based on intensity levels of the phosphor outputs and thusrelative intensity of pumping energies supplied by the various sources.

Several examples utilize doped semiconductor nanophosphors. The upperlimits of the absorption spectra of the exemplary nanophosphors are allat or below 460 nm, for example, around 430 nm although phosphors withsomewhat higher upper limits of their absorption spectra arecontemplated. Other types of semiconductor nanophosphors, nanophosphorsor regular phosphors may be used, and many suitable phosphors of theseother types may have absorption spectra at or below 460 nm. A moredetailed description of several examples of phosphor materials that canbe used is provided later. The system incorporating the device 10 coulduse LEDs or other solid state devices emitting in the UV range, the nearUV range or a bit higher, say up to around or about 460 nm. Fordiscussion purposes, we will assume that the emission spectrum of thesources in the near UV range of 380-420 nm, say 405 nm LEDs.

To provide readers a full understanding, it may help to consider asimplified example of the structure of a solid state source 11, such asa near UV LED type solid state source. FIG. 2 illustrates a simpleexample of a near UV LED type solid state source 11, in cross section.In the example of FIG. 2, the source 11 includes at least onesemiconductor chip, each comprising two or more semiconductor layers 13,15 forming the actual LED. The semiconductor layers 13, 15 of the chipare mounted on an internal reflective cup 17, formed as an extension ofa first electrode, e.g. the cathode 19. The cathode 19 and an anode 21provide electrical connections to layers of the semiconductor chipdevice within the packaging for the source 11. In the example, an epoxydome 23 (or similar transmissive part) of the enclosure allows foremission of the electromagnetic energy from the chip in the desireddirection.

In this simple example, the solid state source 11 also includes ahousing 25 that completes the packaging/enclosure for the source.Typically, the housing 25 is metal, e.g. to provide good heatconductivity so as to facilitate dissipation of heat generated duringoperation of the LED. Internal “micro” reflectors, such as thereflective cup 17, direct energy in the desired direction and reduceinternal losses. Although one or more elements in the package, such asthe reflector 17 or dome 23 may be doped or coated with phosphormaterials, phosphor integrated in (on or within) the package is notrequired for remote phosphor or remote semiconductor nanophosphorimplementations as discussed herein. The point here at this stage of ourdiscussion is that the solid state source 11 is rated to emit near UVelectromagnetic energy of a wavelength range at or below 460 nm, such asin the 380-420 nm range—specifically at 405 nm in the illustratedexample.

Semiconductor devices such as the solid state source 11 exhibit emissionspectra having a relatively narrow peak at a predominant wavelength,although some such devices may have a number of peaks in their emissionspectra. Often, manufacturers rate such devices with respect to theintended wavelength of the predominant peak, although there is somevariation or tolerance around the rated value, from device to device.For example, the solid state source 11 in the example of FIGS. 1A-1D and2 is rated for a 405 nm output, which means that it has a predominantpeak in its emission spectra at or about 405 nm (within themanufacturer's tolerance range of that rated wavelength value). However,other devices that have additional peaks in their emission spectra canbe used in the examples described herein.

The structural configuration of the solid state source 11 shown in FIG.2 is presented here by way of example only. Those skilled in the artwill appreciate that any solid state light emitting sources can be used,and the present teachings are not limited to near UV LEDs. Blue LEDs mayalso be used, and LEDs or the like producing other colors of visiblelight may be used if the phosphors selected for a particularimplementation absorb light of those colors. UV LEDs also may be used.In the example of FIG. 2, the LED device is configured as a source of380-420 nm near UV range electromagnetic energy, for example, havingsubstantial energy emissions in that range such as a predominant peak ator about 405 nm.

As discussed herein, applicable solid state light emitting elements orsources essentially include any of a wide range of light emitting orgenerating devices formed from organic or inorganic semiconductormaterials. Examples of solid state light emitting elements includesemiconductor laser devices and the like. Many common examples of solidstate sources, however, are classified as types of “light emittingdiodes” or “LEDs.” This exemplary class of solid state sourcesencompasses any and all types of semiconductor diode devices that arecapable of receiving an electrical signal and producing a responsiveoutput of electromagnetic energy. Thus, the term “LED” should beunderstood to include light emitting diodes of all types, light emittingpolymers, organic diodes, and the like. LEDs may be individuallypackaged, as in the illustrated examples. Of course, LED based devicesmay be used that include a plurality of LEDs within one package, forexample, multi-die LEDs having two, three or more LEDs within onepackage. Those skilled in the art will recognize that “LED” terminologydoes not restrict the source to any particular type of package for theLED type source. Such terms encompass LED devices that may be packagedor non-packaged, chip on board LEDs, surface mount LEDs, and any otherconfiguration of the semiconductor diode device that emits light. Solidstate sources may include one or more phosphors and/or quantum dots,which are integrated into elements of the package or light processingelements of the fixture to convert at least some radiant energy to adifferent more desirable wavelength or range of wavelengths.

Returning to FIG. 1A, the tunable color lighting device 10 allows forthe changing of intensity of emission of visible light by one of morephosphors contained in each light guide 12. Changing the intensity ofenergy that the respective sources supply to the different light guides12 changes the respective pumping energy supplied to the phosphorscontained in the light guides, which in turn changes the levels ofexcitation and thus changes the respective intensities of the emissionsof the excited phosphors. The color or spectrum of energy of theemissions from the solid state source 11 for every light guide isessentially the same (same rating although there may be variations withmanufacturers' tolerances), but the phosphor(s) contained in the lightguides differ from one light guide to the next. The changing ofintensity of a phosphor emission will now be described with reference toFIG. 3.

FIG. 3 shows one of the light guide/phosphor containing optical elementsof the tunable color light emitting device 10. In the example of FIG. 3,two solid state sources 11 are optically coupled to the ends of lightguide 12, although in this case, not via direct contact or index matchedcoupling. The end surfaces 20 of the light guide are specular surfacesfacing back inside the light guide 12. End surfaces 20 a positionedbetween specular surfaces 20 are made of glass or acrylic and allowlight emitted from the solid state sources 11 to pass into the lightguide 12. The light guide 12 is formed of a light transmissive materialhaving an index of refraction that is higher than that of the ambientenvironment, typically air. The element 12 is configured so that mostlight from the sources passes axially through the element or at most isdirected toward a side of the element 12 at a relatively shallow anglewith respect to the sidewall of the element. As a result, total internalreflection (TIR) from the side surface(s) can be realized with thepositioning of the solid state sources in the opening between specularsurfaces 20. Hence, electromagnetic energy of the first emissionspectrum from the sources 11 will pass and reflect back and forth withinthe element 12, but relatively little of that energy will emerge throughthe sidewall(s) of the optical element. Stated another way, the opticalelement 12 is configured and coupled to each source 11 so as to receiveenergy from the source and act as a light guide with respect to theenergy received from the source.

In the examples of FIGS. 1A-1D and 3, the light guides 12 are tubular.Those skilled in the art will recognize that the tubular light guidesmay be made of a variety of materials/structures having the desiredoptical properties. For example, each light guide 12 could be made froma 3M™ Light Pipe, which is filled with a phosphor bearing material 18and appropriately sealed at both ends. The ends sealing the tube wouldhave the reflective coating 20 and the transmissive section 20 a, likethose of FIG. 3. As manufactured by 3M™, a Light Pipe is a transparenttube lined with 3M™ Optical Lighting Film, which is a micro-replicatedprismatic film. The film is transmissive with respect to light strikingthe surface of the film at steep angles, but it is highly reflective tolight striking the surface of the film at shallow angles. In a lightguide 12 implemented using the 3M™ a Light Pipe, light emitted by theLEDs 11 which strikes the film reflects back into the interior of thelight guide and tends to travel along the length of the light guide 12.If not absorbed by a phosphor particle in the material 18 containedwithin the light guide 12, the light may reflect back from the reflector20 a on the opposite tube end and travel the length of the light guideagain, with one or more reflections off the film lining the interiortube surface. However, light generated by phosphor excitations withinthe light guide 12 impacts the film at steeper angles, and the filmallows relatively uniform release along the length of the light guide12.

A variety of conventional phosphors may be contained in the light guides12 in the form of a solid, a liquid or a gas. Also, recently developedquantum dot (Q-dot) phosphors or doped quantum dot (D-dot) phosphors maybe used. Phosphors absorb excitation energy then re-emit the energy asradiation of a different wavelength than the initial excitation energy.For example, some phosphors produce a down-conversion referred to as a“Stokes shift,” in which the emitted radiation has less quantum energyand thus a longer wavelength. Other phosphors produce an up-conversionor “Anti-Stokes shift,” in which the emitted radiation has greaterquantum energy and thus a shorter wavelength. Quantum dots (Q-dots)provide similar shifts in wavelengths of light. Quantum dots are nanoscale semiconductor particles, typically crystalline in nature, whichabsorb light of one wavelength and re-emit light at a differentwavelength, much like conventional phosphors. However, unlikeconventional phosphors, optical properties of the quantum dots can bemore easily tailored, for example, as a function of the size of thedots. In this way, for example, it is possible to adjust the absorptionspectrum and/or the emission spectrum of the quantum dots by controllingcrystal formation during the manufacturing process so as to change thesize of the quantum dots. Thus, quantum dots of the same material, butwith different sizes, can absorb and/or emit light of different colors.For at least some exemplary quantum dot materials, the larger the dots,the redder the spectrum of re-emitted light; whereas smaller dotsproduce a bluer spectrum of re-emitted light. Doped quantum dot (D-dot)phosphors are similar to quantum dots but are also doped in a mannersimilar to doping of a semiconductor. Also, Colloidal Q-Dots arecommercially available from NN Labs of Fayetteville, Ark. and are basedupon cadmium selenide. Doped semiconductor nanophosphors arecommercially available from NN Labs of Fayetteville, Ark. and are basedupon manganese or copper-doped zinc selenide and can be used with UV ornear UV solid state emitters (e.g. LEDs).

The phosphors may be provided in the form of an ink or a paint. In FIG.3, the one or more phosphors 18 are included within the light guide 12.The phosphor 18 is positioned between the solid state emitters 11 withinthe light guide 12. The phosphor material 18 can be a solid, a liquid ora gas contained within the light guide 12, for example, in the form of abearer material in an internal volume of the container/light guide withthe respective phosphor dispersed in that bearer material. The bearermedium preferably is highly transmissive and/or has low absorption tolight of the relevant wavelengths. Clear or translucent materials may beused. Although alcohol, vegetable oil or other media may be used, themedium or bearer material may be a silicon material. If silicone isused, it may be in gel form or cured into a hardened form in thefinished lighting device product. Another example of a suitablematerial, having D-dot type phosphors in a silicone medium, is availablefrom NN Labs of Fayetteville, Ark. A Q-Dot product, applicable as an inkor paint, is available from QD Vision of Watertown Mass.

Each light guide 12 contains a different phosphor. Individual phosphorsor combinations thereof may be used in each light guide 12 to produce arelatively pure or mono-chromatic light of different colors. At least ina device using three (FIG. 1C), four (FIG. 1D) or more phosphors inrespective containers/light guides, the device 10 can be controlled toprovide a wide range of different selectable colors, encompassing muchof the gamut of visible light, by controlling relative different coloremission levels of the different phosphors in the different light guides12.

For further discussion of this example, we will assume that the eachlight guide 12 forms a container filled with a gaseous or liquidmaterial bearing a different one or more phosphors dispersed therein,where the phosphor(s) in each respective light guide 12, when excited,produces visible light of different respective color emission spectrumthat is at least substantially pure. Tri-color examples might utilize ared (R) emitting phosphor in one light guide 12, a green (G) emittingphosphor in another light guide 12 and a blue (B) emitting phosphor thethird light guide 12. A four-color example might use RGB plus anotherphosphor for emitting another pure color of visible light. Of coursecombinations of phosphors for emitting other three, four or more colorsmay be used in a corresponding numbers of light guides. Also, forfurther discussion, we will assume that the solid state source 11 is anear UV emitting LED, such as a 405 nm LED or other type of LED rated toemit somewhere in the wavelength range of 380-420 nm. In any case, eachphosphor is of a type excited in response to at least the near UVelectromagnetic energy from the LED or LEDs 11 forming the solid statesource in our example.

When so excited, each phosphor in the tunable lighting device 10re-emits visible light of a different relatively pure color. At least inexamples using semiconductor nanophosphors, particularly dopedsemiconductor nanophosphors, each such emission spectrum hassubstantially no overlap with absorption spectra of the particularphosphors. As will be discussed more later, the emission spectra of thephosphors are relative pure or monochromatic colors of light, ascompared to relatively broad spectra as might be used if the device wereintended to produce tunable white light outputs. However, even therelatively pure emission spectra for the variable color light outputdevices tend to be somewhat broader than the narrow spectrum emissionsfrom the LEDs 11. When excited to various selected levels by theselectable levels of electromagnetic energy received from the differentLED sources 11, the phosphors together produce visible light output forthe device 10 of a desired color within the operating gamut encompassedby the points corresponding to the individual phosphor emissions. Atleast in examples of lighting devices using three, four or morecontainers 12 with respectively different pure color emitting phosphors,such devices can selectively output combined light output of a widerange of different selectable colors encompassing much of the gamut ofvisible light.

To appreciate the use of phosphors producing substantially pure coloremissions when excited, it may be helpful to consider some examples.FIGS. 4-6 represent simulations with regard to color performance. Thesimulations are structured for ease of illustration and understanding ofpoints considered herein, however, it is believed that there are avariety of types of phosphors available that would exhibit fairlysimilar performance and could be used to provide fairly similar colortuning performance in a lighting device like any of those disclosedherein.

The drawings simulate three different examples of sets of phosphors withdifferent degrees or levels of purity of the color output, with FIGS.4A-4C representing a lower set of levels of color purity, FIGS. 5A-5Crepresenting a middle set of levels of color purity, and FIGS. 6A-6Crepresenting a higher set of levels of color purity. In these examples,we will assume the use of four phosphors, a red (R) emitting phosphor, agreen (G) emitting phosphor, a blue (B) emitting phosphor, and a fourthcolor phosphor.

FIG. 4A is a table showing some of the data of the first simulation. Thered (R) phosphor exhibits an emission peak at or around 650 nm, thegreen (G) phosphor exhibits an emission peak at or around 520 nm, theblue (B) phosphor exhibits an emission peak at or around 450 nm, and thefourth color phosphor exhibits an emission peak at or around 550 nm(between the peaks for the green and red emissions).

FIG. 4B shows the simulated emission spectra of the four phosphors. Forsimulation purposes, we have assumed that each phosphor emission spectratakes the form of a regular bell-shaped curve, for ease of illustrationand discussion. Each bell-shaped emission spectra has a width,corresponding to one standard deviation. As shown in the table of FIG.4A, in this first example, we have assumed that emission spectra of thefour phosphors all have a width of 45 nm. FIG. 4B in turn shows the fourbell shaped emission spectra simulated to have widths of 45 nm.

The last line of the table of FIG. 4A in turn shows the color purity forthe colors of the four phosphor emissions in this first exemplarysimulation. As shown, the red (R) phosphor exhibits color purity of0.678, the green (G) phosphor exhibits a color purity of 0.279, the blue(B) phosphor exhibits a color purity of 0.731, and the fourth colorphosphor exhibits a color purity of 0.532.

FIG. 4C shows the CIE color chart with the black body curve; and on thatchart, the drawing shows the color points corresponding to the fourcolor emissions of the width and color purities of FIGS. 4A and 4B. Thefour points represent the vertices of the operating gamut of combinedcolor outputs that may be achieved by variable intensity excitations ofphosphors exhibiting emissions spectra like those of FIG. 4B. The CIEchart (outer curved boundary) represents the gamut of light colorvisible to humans. Stated another way, with phosphors producingemissions of spectra approximating those in the simulation, a lightingdevice can selectively output substantially any color on or inside afour sided polygon on the chart bounded/defined by the four colorvertices.

For example, a lighting device using phosphors having emission spectraapproximating the simulations of FIGS. 4A to 4C would be able to producecolors corresponding to the four points. With the sources for pumpingthe other three phosphors off, the device would output only red (R)phosphor emission, with the exemplary bell-shaped spectrum centered onthe peak at or around 650 nm in FIG. 4B, which corresponds to thecircular vertex on the CIE chart in FIG. 4C. Similarly, with the sourcesfor pumping the other three phosphors off, the device would output onlygreen (G) phosphor emission centered on a peak at or around 520 nm inFIG. 4B, which corresponds to the diamond-shaped vertex on the CIE chartin FIG. 4C. With the sources for pumping the other three phosphors off,the device would output only blue (B) phosphor emission centered arounda peak at or around 450 nm in FIG. 4B, which corresponds to thesquare-shaped vertex on the CIE chart in FIG. 4C. Similarly, with thesources for pumping the other three phosphors off, the device wouldoutput only the fourth color phosphor emission centered around a peak ator around 550 nm in FIG. 4B, which corresponds to the triangular vertexon the CIE chart in FIG. 4C. Other settings with two, three or four ofthe phosphors pumped to various excitations levels would result in colorlight output at various points on the chart within the boundary of thepolygon defined by the four color vertices.

As shown, the vertices in the example of FIG. 4C surround a middlesection of the visible color gamut, including the black body curve.Points on or around the black body curve represent many color conditionsthat a person would perceive as white. Hence, a lighting device usingphosphors having emission spectra approximating the simulations of FIGS.4A to 4C would be able to produce a range of white light of variouscolor temperatures on or around points on the black body curve. However,such a lighting device would also be able to produce a range of colorsthat would likely not be perceived as white. Points out closer to theedge of the color chart would have a more specific hue and would appearmore saturated to a human observer.

FIGS. 5A, 5B and 5C show similar data, phosphor emissions spectra andvertices of the operating gamut within the CIE color chart for thevisible light gamut, for a different set of four simulated phosphoremissions. Of note, this second set of simulated phosphor emissions hasthe same colors/wavelengths for the four phosphor emissions, but forthis example, we assumed that each bell-shaped emission spectra has awidth, corresponding to one standard deviation, of 30 nm (see FIG. 5A).FIG. 5B in turn shows the four bell shaped emission spectra simulated tohave widths of 30 nm, that is to say, clearly narrower than the emissionspectra depicted in FIG. 4B.

The last line of the table of FIG. 5A in turn shows the color purity forthe colors of the four phosphor emissions in this first exemplarysimulation. As shown, the red (R) phosphor exhibits color purity of0.834, the green (G) phosphor exhibits a color purity of 0.493, the blue(B) phosphor exhibits a color purity of 0.887, and the fourth colorphosphor exhibits a color purity of 0.736. As shown by comparison of thedata of FIGS. 4A and 5A, the second set of phosphor emissions exhibitingthe narrower emissions spectra represents purer color emissions.

FIG. 5C shows the CIE color chart with the black body curve; and on thatchart, the drawing shows the color points corresponding to the fourcolor emissions of the width and color purities of FIGS. 5A and 5B.Again, the four points represent the vertices of the operating gamut ofcombined color outputs that may be achieved by variable intensityexcitations of phosphors exhibiting emissions spectra like those of FIG.5B. The CIE chart (outer curved boundary) represents the gamut of lightcolor visible to humans. Stated another way, with phosphors producingemissions of spectra approximating those in the simulation, a lightingdevice can selectively output substantially any color on or inside afour sided polygon on the chart bounded/defined by the four colorvertices.

A lighting device using phosphors having emission spectra approximatingthe simulations of FIGS. 5A to 5C would be able to produce colorscorresponding to the four points. As can be seen by comparing FIG. 5C toearlier FIG. 4C, as the phosphor emission spectra become more pure, thespectra from the phosphor emissions effectively move out closer to theedges of the CIE color chart. This effectively expands the operatinggamut of the device using such phosphors to encompass more of thevisible light gamut represented by the outer boundary on the CIE colorchart. Such devices can selectively output combined light of a widerange of different selectable colors encompassing much of the gamut ofvisible light.

With the sources for pumping the other three phosphors off, the devicewould output only red (R) phosphor emission, with the exemplarybell-shaped spectrum centered on the peak at or around 650 nm in FIG.5B, which corresponds to the circular vertex on the CIE chart in FIG.5C. Similarly, with the sources for pumping the other three phosphorsoff, the device would output only green (G) phosphor emission centeredon a peak at or around 520 nm in FIG. 5B, which corresponds to thediamond-shaped vertex on the CIE chart in FIG. 5C. With the sources forpumping the other three phosphors off, the device would output only blue(B) phosphor emission centered around a peak at or around 450 nm in FIG.5B, which corresponds to the square-shaped vertex on the CIE chart inFIG. 5C. Similarly, with the sources for pumping the other threephosphors off, the device would output only the fourth color phosphoremission centered around a peak at or around 550 nm in FIG. 5B, whichcorresponds to the triangular vertex on the CIE chart in FIG. 5C. Othersettings with two, three or four of the phosphors pumped to variousexcitations levels would result in color light output at various pointson the chart within the boundary of the polygon defined by the fourcolor vertices.

Again, the vertices in the example of FIG. 5C surround a middle sectionof the visible color gamut, including the black body curve. Points on oraround the black body curve represent many color conditions that aperson would perceive as white. Hence, a lighting device using phosphorshaving emission spectra approximating the simulations of FIGS. 5A to 5Cwould be able to produce a range of white light of various colortemperatures on or around points on the black body curve. However, sucha lighting device would also be able to produce a range of colors thatwould likely not be perceived as white. Points out closer to the edge ofthe color chart would have a more specific hue and would appear moresaturated to a human observer. In that regard, the vertices in theexample of FIG. 5C define an operating gamut of the device covering awider range of visible colors, including more of the highly saturatedcolors out nearer the boundary of the visible spectrum.

FIGS. 6A, 6B and 6C show similar data, phosphor emissions spectra andvertices of the operating gamut within the CIE color chart for thevisible light gamut, for another set of four simulated phosphoremissions. Of note, this third set of simulated phosphor emissions hasthe same colors/wavelengths for the four phosphor emissions, but forthis example, we assumed that each bell-shaped emission spectra has awidth, corresponding to one standard deviation, of 15 nm (see FIG. 6A).FIG. 6B in turn shows the four bell shaped emission spectra simulated tohave widths of 30 nm, that is to say, clearly narrower than the emissionspectra depicted in FIG. 4B or 5B.

The last line of the table of FIG. 6A in turn shows the color purity forthe colors of the four phosphor emissions in this first exemplarysimulation. As shown, the red (R) phosphor exhibits color purity of0.960, the green (G) phosphor exhibits a color purity of 0.815, the blue(B) phosphor exhibits a color purity of 0.977, and the fourth colorphosphor exhibits a color purity of 0.919. As shown by comparison of thedata of FIGS. 4A and 6A, the third set of phosphor emissions exhibitingthe narrower emissions spectra represents purer color emissions.

FIG. 6C shows the CIE color chart with the black body curve; and on thatchart, the drawing shows the color points corresponding to the fourcolor emissions of the width and color purities of FIGS. 6A and 6B.Again, the four points represent the vertices of the operating gamut ofcombined color outputs that may be achieved by variable intensityexcitations of phosphors exhibiting emissions spectra like those of FIG.6B. The CIE chart (outer curved boundary) represents the gamut of lightcolor visible to humans. Stated another way, with phosphors producingemissions of spectra approximating those in the simulation, a lightingdevice can selectively output substantially any color on or inside afour sided polygon on the chart bounded/defined by the four colorvertices.

A lighting device using phosphors having emission spectra approximatingthe simulations of FIGS. 6A to 6C would be able to produce colorscorresponding to the four points. With the sources for pumping the otherthree phosphors off, the device would output only red (R) phosphoremission, with the exemplary bell-shaped spectrum centered on the peakat or around 650 nm in FIG. 6B, which corresponds to the circular vertexon the CIE chart in FIG. 6C. Similarly, with the sources for pumping theother three phosphors off, the device would output only green (G)phosphor emission centered on a peak at or around 520 nm in FIG. 6B,which corresponds to the diamond-shaped vertex on the CIE chart in FIG.6C. With the sources for pumping the other three phosphors off, thedevice would output only blue (B) phosphor emission centered around apeak at or around 450 nm in FIG. 6B, which corresponds to thesquare-shaped vertex on the CIE chart in FIG. 6C. Similarly, with thesources for pumping the other three phosphors off, the device wouldoutput only the fourth color phosphor emission centered around a peak ator around 550 nm in FIG. 6B, which corresponds to the triangular vertexon the CIE chart in FIG. 6C. Other settings with two, three or four ofthe phosphors pumped to various excitations levels would result in colorlight output at various points on the chart within the boundary of thepolygon defined by the four color vertices.

As can be seen by comparing FIG. 6C to earlier FIGS. 4C and 5C, as thephosphor emission spectra become more pure, the spectra from thephosphor emissions effectively move out closer to the edges of the CIEcolor chart. In the example of FIG. 6C, the red and blue are out on ornear a point on the outer boundary of the visible gamut of the CIE colorchart. The fourth color also is near a point on the outer boundary ofthe visible gamut of the CIE color chart. Even the blue vertex is outnearer the edge of the visible light gamut than in the earlier examples.

As shown by the comparison to the earlier charts, the increased purityof the emission colors further expands the operating gamut of the deviceusing such phosphors to encompass more of the visible light gamutrepresented by the outer boundary on the CIE color chart. Again, thevertices in the example of FIG. 6C surround a middle section of thevisible color gamut, including the black body curve. Points on or aroundthe black body curve represent many color conditions that a person wouldperceive as white. Hence, a lighting device using phosphors havingemission spectra approximating the simulations of FIGS. 6A to 6C wouldbe able to produce a range of white light of various color temperatureson or around points on the black body curve. However, such a lightingdevice would also be able to produce a range of colors that would likelynot be perceived as white. Such devices can selectively output combinedlight of a wide range of different selectable colors encompassing muchof the gamut of visible light. Points out closer to the edge of thecolor chart would have a more specific hue and would appear moresaturated to a human observer. In that regard, the vertices in theexample of FIG. 6C define an operating gamut of the device covering ahigh percentage of the visible colors, including many highly saturatedcolors out near the boundary of the visible spectrum.

As noted earlier, FIGS. 4-6 represent simulated phosphor emissions.However, phosphors, nanophosphors, semiconductor nanophosphors and dopedsemiconductor nanophosphors are available; and many such phosphors maybe chosen and used in light guides or other container elements in alighting device like 10 that can achieve performance generally similarto that of one or more of the simulations of FIGS. 4-6.

FIG. 7A depicts measured spectra of emissions from three exemplaryphosphors, in this case, for red (R), green (G) and blue (B) emissions.For convenience, the measurements of phosphor emissions were taken froma flat screen monitor using a spectrometer. The monitor was driven toemit only red (R), while the spectrometer measured the spectrum of theoutput. Similarly, the monitor was driven to emit only green (G), whilethe spectrometer measured the spectrum of the output; and the monitorwas driven to emit only blue (B) while the spectrometer measured thespectrum of the output. However, the spectra for RGB emissions shown inFIG. 7A represent actual measured data of commercially availablephosphors, and such phosphors are among the broad general class ofphosphors having sufficiently pure emission spectra to enable their usedin the variable color lighting devices discussed herein.

The scale of the drawing in FIG. 7A is somewhat larger than used inFIGS. 4B, 5B and 6B. As shown, the spectra are not as uniform as in thesimulations but still generally can be viewed as centered around aparticular wavelength. For example, the blue phosphor emission spectrumis roughly centered around 450 nm, although there is a narrow spikesomewhat below 450 nm. The blue emission spectrum runs from 400 to 500nm. The green emission spectrum in this example runs from about 530 upto around 565 nm, with a pronounced central peak at about 545 nm. Thered emission spectrum in this example runs from 600 up to around 630 nm,with a pronounced central peak at about 615 nm. As shown, the green andred emission spectra are quite narrow. The blue emission spectrum issomewhat broader, but even that spectrum has a very narrow main peak.

FIG. 7B shows the CIE color chart with the black body curve; and on thatchart, the drawing shows the color points corresponding to the threecolor emissions spectra shown in FIG. 7A. Here, the three pointsrepresent the vertices of the operating gamut of combined color outputsthat may be achieved by variable intensity excitations of the phosphorsfor purposes of this example. In the example, the blue phosphor emissionspectrum roughly centered around 450 nm is represented by the triangularshaped vertex, the green emission centered around 545 nm is representedby the circular shaped vertex, and the red emission spectrum centeredaround 630 nm is represented by the square vertex. A lighting deviceusing phosphors having emission spectra as shown in FIG. 7A would beable to produce colors corresponding to the three points on the diagramof FIG. 7B as well as points within the triangular operating gamutdefined by those three points. Such devices can selectively outputcombined light of a wide range of different selectable colorsencompassing much of the gamut of visible light.

With the sources for pumping the other two phosphors off, the devicewould output only blue (B) phosphor emission, with the emission spectrumroughly centered around 450 nm, like that shown in FIG. 7A (triangularvertex in FIG. 7B). Similarly, with the sources for pumping the othertwo phosphors off, the device would output only green (G) phosphoremission centered on a peak at or around 545 nm in FIG. 7A (circularvertex in FIG. 7B), and with the sources for pumping the other twophosphors off, the device would output only red (R) phosphor emissioncentered around a peak at or around 630 nm in FIG. 7A (square-shapedvertex in FIG. 7B). Other settings with two or three of the phosphorspumped to various excitations levels would result in color light outputat various points on the chart within the boundary of the triangledefined by the three color vertices.

As shown in FIG. 7B, the three vertices of the operating gamut arerelatively close to the outer boundary of the visible spectrum. In thisway, much like the simulation of FIGS. 6A-6C, the actual tri-colorphosphors in the example of FIGS. 7A and 7B create a tunable coloroutput that encompasses relatively white light on and around the blackbody curve as well as a range of colors of more specific hues, many ofwhich exhibit relatively high color saturation out near the boundary ofthe visible spectrum.

The example of FIGS. 7A and 7B used just one set of phosphors found in aparticular display device that was available for test measurements.However, a wide range of phosphors are available. As outlined above,many of the nanophosphors can be tailored to particular applications, bycareful growth to a desired nano-crystal size and or by specific dopingof the semiconductor materials. Hence, persons of skill in the art willappreciate that phosphors can be selected for a particular lightingdevice product that can achieve spectra that are even closer to those inthe simulations of FIGS. 4A-6C than the phosphors represented by themeasured spectra of FIGS. 7A and 7B.

There may be commercial reasons for selecting phosphors that exhibitrelatively large Stokes shift, such as doped semiconductornanophosphors. Large shifts tend to separate the emission spectra ofseveral phosphors used in a particular device 10 from the absorptionspectra of the phosphors. As a result, the phosphors tend to exhibitrelatively little or no re-absorption. Stated another way, light emittedby a phosphor does not tend to be absorbed by that same phosphor orother phosphors in the device.

If the absorption spectra are in the range of around 460 nm and below,there may be relatively little ambient light that falls within theabsorption spectra. As a result, when the sources 11 of the device 10are off, the phosphors at 18 in the various light guides 12 will emitlittle or no light. If the bearer materials are color neutral, e.g.clear or translucent, then when the respective source(s) are off thematerial with phosphor dispersed therein inside each light guide will besimilarly color neutral, that is to say, will exhibit littler or noperceptible tint. For example, if the phosphor bearing material isclear, when the respective source 11 is off, the material with thephosphor dispersed therein will appear clear inside the light guide 12.

Alternative examples of tunable color light emitting devices and/orsystems are shown in FIGS. 8 and 9. If used with phosphors providingrelatively pure individual color emissions, these examples could producea wide range of colors including many colors of relatively highsaturation, as well as white, similar to the examples discussed above.

In the example of FIG. 8, device 50 (without the electronics of thesystem) includes the solid state sources 11, which again for purposes ofthe example are rated to emit 405 nm near UV energy toward the lightguides 12. The device is configured as a downlight type fixture similarto that in overall design of a traditional downlight fixture. Thelighting device 50 uses light guides/containers in an opticalintegrating volume. The light guides could be tubular, as in earlierexamples. However, other shapes are possible. For a round type offixture, the light guides may be disk-shaped.

Energy from the sources impacts on and excites the phosphors 18contained within the light guides 12. Although two light guides 12 areillustrated in FIG. 8, this example could use just one light guide 12 orcould utilize more light guides 12. Some phosphor emissions from thelight guides are diffusely reflected by the dome surface 30 b backtoward an optical aperture 30 a. Much of the reflected 405 nm energy inturn impacts on the phosphors 18. When so excited, the phosphorparticles re-emit electromagnetic energy but now of the wavelengths forthe desired visible spectrum for the intended light output. The visiblelight produced by the excitation of the phosphor particles diffuselyreflects one or more times off of the reflective inner surface 30 b ofthe dome forming cavity 30. This diffuse reflection within the cavityintegrates the light produced by the phosphor excitation to formintegrated light of the desired color at the optical aperture 30 aproviding a substantially uniform output distribution of integratedlight (e.g. substantially Lambertian). Solid state sources 11 a can beprovided facing towards cavity 30. Light emitted from solid statesources 11 a passes through the light guide(s) 12 once to impact thephosphor contained within the light guide, whereas light from solidstate sources 11 passes through the light guides 12 multiple times andimpacts the phosphor multiple times.

The optical aperture 30 a may serve as the light output of the device50, directing optically integrated light of the desired color andrelatively uniform intensity distribution to a desired area or region tobe illuminated in accord with a particular general lighting applicationof the system. Some masking 30 c exists between the edge of the aperture30 a and the outside of the guides 12. The optical cavity is formed by acombination of the reflective dome 30, the reflective ends (or sides ifcircular) of the guides 12 and the reflective surface of the mask 30 c.

The optical cavity can be a solid that is light transmissive(transparent or translucent) of an appropriate material such as acrylicor glass bounded by a diffuse reflector. The optical cavity can alsocontain a liquid. If a solid is used, the solid forms an integratingvolume because it is bounded by reflective surfaces which form asubstantial portion of the perimeter of the cavity volume. Statedanother way, the assembly forming the optical integrating volume in thisexample comprises a light transmissive solid and a reflector having areflective interior surface 30 b.

The optical integrating volume is a diffuse optical processing elementused to convert a point source input, typically at an arbitrary pointnot visible from the outside, to a virtual source. At least a portion ofthe interior surface of the optical integrating volume exhibits adiffuse reflectivity. Hence, in the example, the surface 30 b has adiffuse type of reflectivity and is highly reflective (90% or more andpossibly 98% or higher). The optical integrating volume may have variousshapes. The illustrated cross-section would be substantially the same ifthe cavity is hemispherical or if the cavity is semi-cylindrical with alateral cross-section taken perpendicular to the longitudinal axis ofthe semi-cylinder. For purposes of the discussion, the opticalintegrating volume in the device 50 is assumed to be hemispherical ornearly hemispherical. Hence, the solid at least above the light guidesin the example would be a hemispherical or nearly hemispherical solid,and the reflector would exhibit a slightly larger but concentrichemispherical or nearly hemispherical shape at least along its internalsurface, although the hemisphere would be hollow but for the fillingthereof by the solid. In practice, the reflector may be formed of asolid material or as a reflective layer on a solid substrate and thesolid molded into the reflector. Parts of the light emission surface ofthe solid (lower flat surface in the illustrated orientation) are maskedby the reflective surface 30 c. At least some substantial portions ofthe interior facing reflective surfaces 30 c are diffusely reflectiveand are highly reflective, so that the resulting optical integratingvolume has a diffuse reflectivity and is highly reflective.

In this example, the optical integrating volume forms an integratingtype optical cavity. The optical integrating volume has a transmissiveoptical passage or aperture 30 a. Emission of light from the phosphorsand/or extra LEDs 11 a is reflected and diffused within the interior ofthe optical integrating volume and directed into a region to facilitatea humanly perceptible general lighting application for the device 50.

For some applications, the device 50 includes an additional deflector orother optical processing element as a secondary optic, e.g. todistribute and/or limit the light output to a desired field ofillumination. In the example of FIG. 8, the fixture part of the device50 also utilizes a conical deflector 30 d having a reflective innersurface, to efficiently direct most of the light emerging from thevirtual light source at optical aperture 30 a into a somewhat narrowfield of illumination. The deflector 30 d has a larger opening at adistal end thereof compared to the end adjacent to the optical aperture30 a. The angle and distal opening size of the conical deflector 30 ddefine an angular field of white light emission from the device 50.Although not shown, the large opening of the deflector may be coveredwith a transparent plate, a diffuser or a lens, or covered with agrating, to prevent entry of dirt or debris through the cone into thesystem and/or to further process the output white light. Alternatively,the deflector could be filled with a solid light transmissive materialof desirable properties.

The conical deflector 30 d may have a variety of different shapes,depending on the particular lighting application. In the example, wherethe cavity 30 is hemispherical and the optical aperture 30 a iscircular, the cross-section of the conical deflector is typicallycircular. However, the deflector may be somewhat oval in shape. Even ifthe aperture 30 a and the proximal opening are circular, the deflectormay be contoured to have a rectangular or square distal opening. Inapplications using a semi-cylindrical cavity, the deflector may beelongated or even rectangular in cross-section. The shape of the opticalaperture 30 a also may vary, but will typically match the shape of theopening of the deflector 30 d. Hence, in the example the opticalaperture 30 a would be circular. However, for a device with asemi-cylindrical cavity and a deflector with a rectangularcross-section, the optical aperture may be rectangular.

The deflector 30 d comprises a reflective interior surface between thedistal end and the proximal end. In some examples, at least asubstantial portion of the reflective interior surface of the conicaldeflector exhibits specular reflectivity with respect to the integratedlight energy. For some applications, it may be desirable to constructthe deflector 30 d so that at least some portions of the inner surfaceexhibit diffuse reflectivity or exhibit a different degree of specularreflectivity (e.g. quasi-specular), so as to tailor the performance ofthe deflector 30 d to the particular application. For otherapplications, it may also be desirable for the entire interior surfaceof the deflector to have a diffuse reflective characteristic.

The lighting device 50 outputs selectable color light produced by thesolid state sources' 11 excitation of the phosphor materials 18. Thephosphors 18 can be doped semiconductor nanophosphors or other phosphorsof the types discussed above. The tunable color lighting device 50 coulduse a variety of different combinations of phosphors to produce adesired range color outputs. Different lighting devices (or systemsincluding such devices) designed for different ranges of color outputlight and/or different degrees of available tuning may use differentcombinations of phosphors such as different combinations of two, three,four or more phosphors as discussed earlier. Depending on the selectednumber and types of phosphors, the output may correspond to one of theoperating gamuts (defined by the phosphor color vertices) in FIGS. 4C,5C, 6C and 7B.

The tunable color lighting device 50 may be coupled to a controlcircuit, to form a lighting system. Although not shown in FIG. 8 forconvenience, such a controller would be coupled to the LED typesemiconductor chip in each source 11, for establishing output intensityof electromagnetic energy of the respective LED sources 11. The controlcircuit may include one or more LED driver circuits for controlling thepower applied to one or more sources 11 and thus the intensity of energyoutput of the source and thus of the system overall. The control circuitmay be responsive to a number of different control input signals, forexample to one or more user inputs, to turn power ON/OFF and/or to set adesired intensity level for the white light output provided by thedevice 50. However, the control circuit can also adjust the drives tothe sources 11 to tune the color of the light output as in the earlierexamples. The color tuning can be responsive to user input or canimplement automatic control algorithms, e.g. to change color temperatureof the white light output for different times of day or to change colorover time for mood or attractive lighting applications.

Turning now to system 60 in FIG. 9, another tunable color light emittingsystem is described. A fixture portion of the system is shown incross-section (although some cross-hatching thereof has been omitted forease of illustration). The circuit elements are shown in functionalblock form. The system 60 utilizes solid state sources 11, for emittinglight energy, for example, of a wavelength in the near UV range, in thiscase in the 380-420 nm range.

The tunable color light system 60 includes a light guide configurationsimilar to that in FIG. 8. For example, for a round fixture, the lightguides may be disk-shaped. A reflector 12 aa is positioned below thebottom guide 12 to reflect phosphor emissions aimed downward back up aspart of the combined light output shown at the top in the illustratedorientation. The lighting system could be configured for a generallighting application. Examples of general lighting applications includedownlighting, task lighting, “wall wash” lighting, emergency egresslighting, as well as illumination of an object or person in a region orarea intended to be occupied by one or more people. A task lightingapplication, for example, typically requires a minimum of approximately20 foot-candles (fcd) on the surface or level at which the task is to beperformed, e.g. on a desktop or countertop. In a room, where the lightfixture is mounted in or hung from the ceiling or wall and oriented as adownlight, for example, the distance to the task surface or level can be35 inches or more below the output of the light fixture. At that level,the light intensity will still be 20 fcd or higher for task lighting tobe effective. Of course, the system 60 of FIG. 9 may be used in otherapplications, such as vehicle headlamps, flashlights, etc.

System 60 has a reflector 12 a with a reflective surface arranged toreceive at least some pumped light from the phosphor material 18 fromthe light guides 12. If the phosphor material is housed, the materialforming the walls of the housing exhibit high transmissivity and/or lowabsorption to light of the relevant wavelengths. The walls of thehousing for the phosphor material 18 may be smooth and highlytransparent or translucent, and/or one or more surfaces may have anetched or roughened texture.

The disclosed system 60 may use a variety of different structures orarrangements for the reflector 12 a. For efficiency, the reflectivesurface of the reflector 12 a should be highly reflective. Thereflective surface may be specular, semi or quasi specular, or diffuselyreflective. In the example, the emitting region of light guides 12 fitsinto or extends through an aperture in a proximal section of thereflector 12 a. In the orientation illustrated, white light from thephosphor excitation, including any white light emissions reflected bythe surface of reflector 12 a are directed upwards, for example, forlighting a ceiling so as to indirectly illuminate a room or otherhabitable space below the fixture. The orientation shown, however, ispurely illustrative.

The system 60 outputs combined light of selected color produced by thesolid state sources 11 exciting the phosphor materials 18 and may becontrolled to selectively exhibit one or more of colors in the rangesdiscussed above. The phosphors 18 can be doped semiconductornanophosphors or other phosphors of the types discussed above relativeto FIGS. 4C, 5C, 6C and 7B. The tunable color light emission system 60could use a variety of different combinations of phosphors to produce adesired tunable color performance in the output. Different lightingsystems designed for different color output light and/or differentdegrees of available tuning may use different combinations of phosphorssuch as different combinations of two, three, four or more of thephosphors as discussed earlier. Depending on the selected number andtypes of phosphors, the output may correspond to one of the operatinggamuts (defined by the phosphors color vertices) in FIGS. 4C, 5C, 6C and7B.

The tunable color light emission system 60 includes a control circuit 33coupled to the LED type semiconductor chip in the source 11, forestablishing output intensity of electromagnetic energy output of eachof the LED sources 11. Similar control circuits could be used with thedevices 10 and 50 in the earlier examples. The control circuit 33typically includes a power supply circuit coupled to a voltage/currentsource, shown as an AC power source 35. Of course, batteries or othertypes of power sources may be used, and the control circuit 33 willprovide the conversion of the source power to the voltage/currentappropriate to the particular solid state sources utilized in aparticular system. The control circuit 33 includes one or more LEDdriver circuits for controlling the power applied to one or more sources11 and thus the intensity of energy output of the source and thus of thesystem overall. The control circuit 33 may be responsive to a number ofdifferent control input signals, for example to one or more user inputsas shown by the arrow in FIG. 9, to turn power ON/OFF and/or to set adesired intensity level for the white light output provided by thesystem 60. However, the control circuit can also adjust the drives tothe sources 11 to tune the color of the light output as in the earlierexamples. The color tuning can be responsive to user input or canimplement automatic control algorithms, e.g. to change the colortemperature of the white light output for different times of day.

FIG. 10 illustrates yet another tunable color light emission system incross section. Here the system is in the form of a lamp product, in aform factor somewhat similar to a form factor of an incandescent lamp.The exemplary system 130 may be utilized in a variety of lightingapplications. The solid state sources 11 are similar to those previouslydiscussed. In the example, the sources comprise a plurality of lightemitting diode (LED) devices, although other semiconductor devices mightbe used. Hence, in the example of FIG. 10, each of the three separatelycontrollable sources 11 takes the form of a number of LEDs (e.g. threeLEDs for each source as shown in the view of FIG. 11).

It is contemplated that the LEDs 11 could be of any type rated to emitenergy of wavelengths from the blue/green region around 460 nm down intothe UV range below 380 nm. Exemplary nanophosphors have absorptionspectra having upper limits around 430 nm, although other phosphors maybe used that have somewhat higher limits on the wavelength absorptionspectra and therefore may be used with LEDs or other solid state devicesrated for emitting wavelengths as high as say 460 nm. In the presentexample, the LEDs 11 are near UV LEDs rated for emission somewhere inthe 380-420 nm range, such as the 405 nm LEDs discussed earlier,although UV LEDs could be used with the nanophosphors.

As in the earlier examples, the phosphor-centric tunable lighting system130 could utilize two, three or more phosphors that produce a relativelypure or mono-chromatic light of respectively different colors, so thatthe lamp 130 can be controlled to provide a wide range of differentcolors, encompassing much of the gamut of visible light.

Here, for discussion purposes two, three or more types of semiconductornanophosphors are used in the system 130 to convert energy from therespective sources into visible light of appropriate spectra to producea desired range of colors in the visible light output of the lamp. Thesemiconductor nanophosphors again are remotely deployed, in that theyare outside of the individual device packages or housings of the LEDs11. For this purpose, the exemplary system includes a number of opticalelements in the form of phosphor containers formed of opticallytransmissive material coupled to receive near UV electromagnetic energyfrom the LEDs 11 forming the solid state sources. Each containercontains a material, which at least substantially fills the interiorvolume of the container. For example, if a liquid is used, there may besome gas in the container as well, although the gas should not includeoxygen as oxygen tends to degrade the nanophosphors. The material may bea solid or a gas. In this example, the system includes at least onesemiconductor nanophosphor dispersed in the material in each container.

As noted, the material may be a solid, although liquid or gaseousmaterials may help to improve the florescent emissions by thenanophosphors in the material. For example, alcohol, oils (synthetic,vegetable, silicon or other oils) or other liquid media may be used. Asilicone material, however, may be cured to form a hardened material, atleast along the exterior (to possibly serve as an integral container),or to form a solid throughout the intended volume. If hardened siliconis used, however, a glass container still may be used to provide anoxygen barrier to reduce nanophosphor degradation due to exposure tooxygen.

If a gas is used, the gaseous material, for example, may be hydrogengas, any of the inert gases, and possibly some hydrocarbon based gases.Combinations of one or more such types of gases might be used.

Similar materials may be used, for example contained in the lightguides, to remotely deploy the phosphors in the earlier examples.

In the illustrated example, three containers 131 are provided, eachcontaining a phosphor bearing material 150. The three containers areenclosed by an outer bulb 133 which provides a desired outputdistribution and form factor, e.g. like a glass bulb of an A-lampincandescent. The glass bulb 133 encloses three optical elements havingthe different nanophosphors, for RGB emissions as in several of theearlier examples. The sources 11 and elements 131 provide sufficientoptical separation to support the desired color tuning, as mentionedearlier. The elements 131 could be light guides as in the earlierexamples but with pumping light entry from only one end and atransmissive or reflective opposite end. In the example, however, eachof the three optical elements is a container 131. The container wall(s)are transmissive with respect to at least a substantial portion of thevisible light spectrum. For example, the glass of each container 131will be thick enough to provide ample strength to contain a liquid orgas material if used to bear the semiconductor nanophosphors insuspension, as shown at 150. However, the material of the container 131will allow transmissive entry of energy from the LEDs 11 to reach thenanophosphors in the material 150 and will allow transmissive output ofvisible light principally from the excited nanophosphors.

Each glass element/container 131 receives energy from the LEDs 11through a surface of the container, referred to here as an optical inputcoupling surface 131 c. The example shows the surface 131 c as a flatsurface, although obviously other contours may be used. Light outputfrom the system 130 emerges through one or more other surfaces of thecontainers 131 and through and outer surface of bulb 133, referred tohere as output surface 133 o. In the example, the bulb 133 here isglass, although other appropriate transmissive materials may be used.For a diffuse outward appearance of the bulb, the output surface(s) 133o may be frosted white or translucent. Alternatively, the output surface133 o may be transparent. The emission surfaces of the containers 131may be may be frosted white or translucent, although the optical inputcoupling surfaces 131 c might still be transparent to reduce reflectionof energy from the LEDs 11 back towards the LEDs.

Although a solid could be used, in this example, each container 131 isat least substantially filled with a liquid or gaseous material 150bearing a different semiconductor nanophosphor dispersed in the liquidor gaseous material 150. The example shows three containers 131containing material 150 bearing nanophosphors for red (R), green (G) andblue (B) emissions, as in several of the earlier light guide examples.The RGB emissions may correspond to RGB spectra discussed above relativeto FIGS. 4-7. Also, for further discussion, we will assume that the LEDs11 are near UV emitting LEDs, such as 405 nm LEDs or other types of LEDsrated to emit somewhere in the wavelength range of 380-420 nm, as inseveral earlier examples. Each of the semiconductor nanophosphors (Red,Green, and Blue) is of a type excited in response to near UVelectromagnetic energy from the LEDs 11 of the solid state source. Whenso excited, each semiconductor nanophosphor re-emits visible light of adifferent spectrum. However, each such emission spectrum hassubstantially no overlap with excitation spectra of the semiconductornanophosphors. When excited by the electromagnetic energy received fromthe LEDs 11, the semiconductor nanophosphors in material 150 in thethree containers 131 together produce visible light output for thesystem 130 through the exterior surface(s) of the glass bulb 133.

The liquid or gaseous material 150 with the semiconductor nanophosphordispersed therein appears at least substantially clear when the system130 is off. For example, alcohol, oils (synthetic, vegetable or otheroils) or other clear liquid media may be used, or the liquid materialmay be a relatively clear hydrocarbon based compound or the like.Exemplary gases include hydrogen gas, clear inert gases and clearhydrocarbon based gases. The doped semiconductor nanophosphors in thespecific examples described below absorb energy in the near UV and UVranges. The upper limits of the absorption spectra of exemplaryphosphors, e.g. doped semiconductor nanophosphors, are all at or around430 nm, however, the exemplary nanophosphors are relatively insensitiveto other ranges of visible light often found in natural or other ambientwhite visible light. Hence, when the system 130 is off, thesemiconductor nanophosphors exhibit little or no light emissions thatmight otherwise be perceived as color by a human observer. Even thoughnot emitting, the particles of the semiconductor nanophosphors may havesome color, but due to their small size and dispersion in the material,the overall effect is that the material 150 appears at leastsubstantially clear to the human observer, that is to say it has littleor no perceptible tint.

The LEDs 11 are mounted on a circuit board 170. The exemplary system 130also includes circuitry 190. Although drive from DC sources iscontemplated for use in existing DC lighting systems, the examplesdiscussed in detail utilize circuitry configured for driving the LEDs 11in response to alternating current electricity, such as from the typicalAC main lines. The circuitry may be on the same board 170 as the LEDs ordisposed separately within the system and electrically connected to theLEDs 11. Electrical connections of the circuitry 190 to the LEDs and thelamp base are omitted here for simplicity. Details of an example ofdrive circuitry are discussed later with regard to FIG. 12. However, asin the earlier examples, independent control of the drive to the threesets of LEDs that separately pump the three different nanophosphors inthe containers 131 allows control of the mix of phosphor produced R, Gand B light, to effectively tune the color of the light output.

A housing 210 at least encloses the circuitry 190. In the example, thehousing 210 together with a base 230 and a face of the glass bulb 133also enclose the LEDs 11. The system 130 has a lighting industrystandard base 230 mechanically connected to the housing and electricallyconnected to provide alternating current electricity to the circuitry190 for driving the LEDs 11.

The base 230 may be any common standard type of lamp base, to permit useof the system 130 in a particular type of electrical socket. Commonexamples include an Edison base, a mogul base, a candelabra base and abi-pin base. The base 230 may have electrical connections for a singleintensity setting or additional contacts in support of three-wayintensity setting/dimming.

The exemplary system 130 of FIG. 10 may include one or more featuresintended to prompt optical efficiency. Hence, as illustrated, the system130 includes a diffuse reflector 250. The circuit board 170 has asurface on which the LEDs 11 are mounted, so as to face toward the lightreceiving surface of the glass bulb 133 containing the nanophosphorbearing material 150. The reflector 250 covers parts of that surface ofthe circuit board 170 in one or more regions between the LEDs 11. FIG.11 is a view of the LEDs 11 and the reflector 250. When excited, thenanophosphors in the material 150 emit light in many differentdirections, and at least some of that light would be directed backtoward the LEDs 11 and the circuit board 170. The diffuse reflector 250helps to redirect much of that light back through the glass bulb 133 forinclusion in the output light distribution. The system may use anynumber of LEDs 11 sufficient to provide a desired output intensity.

There may be some air gap between the emitter outputs of the LEDs 11 andthe facing optical coupling surface 131 c of the containers 131 (FIG.10). However, to improve out-coupling of the energy from the LEDs 11into the light transmissive glass of the containers 131, it may behelpful to provide an optical grease, glue or gel 270 between thesurfaces 131 c of the glass containers 131 and the optical outputs ofthe LEDs 11. This index matching material 270 eliminates any air gap andprovides refractive index matching relative to the material of the glassof each container 131.

The examples also encompass technologies to provide good heatconductivity so as to facilitate dissipation of heat generated duringoperation of the LEDs 11. Hence, the system 130 includes one or moreelements forming a heat dissipater within the housing for receiving anddissipating heat produced by the LEDs 11. Active dissipation, passivedissipation or a combination thereof may be used. The system 130 of FIG.10, for example, includes a thermal interface layer 310 abutting asurface of the circuit board 170, which conducts heat from the LEDs andthe board to a heat sink arrangement 333 shown by way of example as anumber of fins within the housing 210. The housing 210 also has one ormore openings or air vents 350, for allowing passage of air through thehousing 210, to dissipate heat from the fins of the heat sink 333.

The thermal interface layer 310, the heat sink 333 and the vents 350 arepassive elements in that they do not consume additional power as part oftheir respective heat dissipation functions. However, the system 130 mayinclude an active heat dissipation element that draws power to cool orotherwise dissipate heat generated by operations of the LEDs 11.Examples of active cooling elements include fans, Peltier devices or thelike. The system 130 of FIG. 10 utilizes one or more membronic coolingelements. A membronic cooling element comprises a membrane that vibratesin response to electrical power to produce an airflow. An example of amembronic cooling element is a SynJet® sold by Nuventix. In the exampleof FIG. 10, the membronic cooling element 370 operates like a fan or airjet for circulating air across the heat sink 333 and through the airvents 350.

In the orientation illustrated in FIG. 10, white light from thesemiconductor nanophosphor excitation is dispersed upwards andlaterally, for example, for omni-directional lighting of a room from atable or floor lamp. The orientation shown, however, is purelyillustrative. The system 130 may be oriented in any other directionappropriate for the desired lighting application, including downward,any sideways direction, various intermediate angles, etc. In the exampleof FIG. 10, the glass bulb 133 produces a wide dispersion of outputlight, which is relatively omni-directional (except directly downward inthe illustrated orientation). Of course, other bulb shapes may be used.Some bulbs may have some internal reflective surfaces, e.g. tofacilitate a particular desired output distribution of the tunable whitelight.

The system 130 of FIG. 10 has one of several industry standard lampbases 230, shown in the illustration as a type of screw-in base. Theglass bulb 133 exhibits a form factor within standard size, and theoutput distribution of light emitted via the bulb 133 conforms toindustry accepted specifications. Those skilled in the art willappreciate that these aspects of the system facilitate use of it as areplacement for existing systems, such as incandescent lamps and compactflorescent lamps.

The housing 210, the base 230 and components contained in the housing210 can be combined with a bulb and containers in a variety of differentshapes. As such, these elements together may be described as a ‘lightengine’ portion of the system. Theoretically, the engine alone or incombination with a standard sized set of the containers could be modularin design with respect to a variety of different bulb configuration, toallow a user to interchange glass bulbs, but in practice the lamp is anintegral product. The light engine may be standardized across severaldifferent lamp product lines.

As outlined above, the system 130 will include or have associatedtherewith phosphors remotely deployed in multiple containers external tothe LEDs 11 of the solid state source(s). As such, the phosphors arelocated apart from the semiconductor chip of the LEDs 11 used in theparticular lamp 10, that is to say remotely deployed.

The phosphors are dispersed, e.g. in suspension, in a liquid or gaseousmaterial 150, within a container (bulb 133 in the system of FIG. 10).The liquid or gaseous medium preferably exhibits high transmissivityand/or low absorption to light of the relevant wavelengths, although itmay be transparent or somewhat translucent. Although alcohol, oils(synthetic, vegetable, silicon or other oils) or other media may beused, the medium may be a hydrocarbon material, in either a liquid orgaseous state.

In FIG. 10, the system is able to adjust or ‘tune’ the color of theoutput light, by adjusting the levels of emissions of the RGB phosphors.The LEDs are used to pump the three separately contained semiconductornanophosphors (R, G, and B). The system allows for the changing ofintensity of emission of visible light by the three (R, G, B) phosphorsseparately contained phosphors. Changing the intensity of energy thatthe respective sources supply to the different housed phosphors changesthe respective pumping energy supplied to the phosphors, which in turnchanges the levels of excitation and thus changes the respectiveintensities of the RGB emissions of the excited phosphors. The color orspectrum of energy of the emissions from the solid state source 11 isessentially the same (same rating although there may be variations withmanufacturers' tolerances), but the phosphors are different (i.e. R, G,and B), separately contained and excited to independently controllablelevels as in the earlier examples. The color of the combined outputlight varies with changes in the different relative levels of the lightemissions from the three different phosphors. For example, if the RGBphosphors exhibit the emission spectra of FIG. 7A, the operating gamutof the output of the lamp 130 would be defined by the color vertices inthe chart of FIG. 7B.

The drive circuit may be programmed to vary color over time.Alternatively, the drive circuit may receive control signals modulatedon the power received through the standard lamp base.

The sources 11 in the various examples discussed so far may be driven byany known or available circuitry that is sufficient to provide adequatepower to drive the sources at the level or levels appropriate to theparticular lighting application of each particular fixture and to adjustthose levels to provide desired color tuning. Analog and digitalcircuits for controlling operations and driving the sources arecontemplated. Those skilled in the art should be familiar with varioussuitable circuits. However, for completeness, we will discuss an examplein some detail below.

An example of suitable circuitry, offering relatively sophisticatedcontrol capabilities, with reference to FIG. 12. A simpler circuit or asubset of such a circuit would more likely be included inside the lampsystem of FIG. 10. For devices like those of FIGS. 1, 8 and 9, however,circuitry like that of FIG. 12 could be deployed in a separate housinganalogous to the ballast of a florescent light.

The drawing of FIG. 12 is a block diagram of an exemplary tunable colorlight emission system 100, including the control circuitry and LED typesold state light sources. The LEDs and possibly some of the otherelectronic elements of the system could be combined with any of thedevice examples discussed above to form systems, with the LEDs in array111 shown in FIG. 12 serving as the various solid state sources 11. Thecircuitry of FIG. 12 provides digital programmable control of thetunable color light.

In the light engine 101 of FIG. 12, the set of solid state sources, suchas those of UV or near UV light takes the form of a LED array 111. Inthis example, the array 111 comprises 405 nm LEDs arranged in each offour different strings forming lighting channels C1 to C4 for pumping ofRGB phosphors. The array 111 includes three initially active strings ofLEDs, represented by LED blocks 113 (for pumping red phosphors), 115(for pumping green phosphors) and 117 (for pumping blue phosphors).

The strings in this example have the same number of LEDs. LED blocks113, 115 and 117 each comprises 6 LEDs. The LEDs may be connected inseries, but in the example, two sets of 3 series connected LEDs areconnected in parallel to form the blocks or strings of 6 405 nm near UVLEDs 113, 115, 117. The LEDs 113 may be considered as a first channel C1to pump a red emitting phosphor in a first of the containers or lightguides, the LEDs 115 may be considered as a second channel C2 forpumping a green emitting phosphor in a second of the containers or lightguides, whereas the LEDs 117 may be considered as a third channel C3 topump a blue emitting phosphor in a third of the containers or lightguides.

One set of 3 LEDs might be located at each end of a tubular light guidelike in FIGS. 1A and 1C, or the complete set of 6 LEDs might be locatedaround the periphery of a disk-shaped light guide like in FIG. 8 or FIG.9. In FIG. 10 the different sets of 6 LEDs would supply pumping energyto respective containers.

The LED array 111 in this example also includes a number of additionalor ‘other’ LEDs 119. Some implementations may include various colorLEDs, such as specific primary color LEDs, IR LEDs or UV LEDs, forvarious ancillary purposes. Another approach might use the LEDs 119 fora fourth channel of 405 nm LEDs to further control intensity of pumpinganother phosphor in a fourth of the containers or light guides (seesimulations in FIGS. 4-6). In the example, however, the additional LEDs119 are ‘sleepers.’ Although shown for simplicity as a single group 119,there would likely be independently controllable sleepers 119 associatedwith each of the optical elements (light guides or containers) of aparticular tunable color lighting device. Initially, the LEDs 113-117would be generally active and operate in the normal range of intensitysettings, whereas sleepers 119 initially would be inactive. InactiveLEDs are activated when needed, typically in response to feedbackindicating a need for increased output to pump one or more of thephosphors (e.g. due to decreased performance of one, some or all of theoriginally active LEDs 113-117). The set of sleepers 119 may include anyparticular number and/or arrangement of the LEDs as deemed appropriatefor a particular application.

Strings 113, 115, and 117 may be considered a solid state light emittingelement or ‘source’ coupled to supply near UV light so as to pump orexcite the red, green, blue, phosphors, respectively, in opticalelements of a lighting device. Each string comprises a plurality oflight emitting diodes (LEDs) serving as individual solid state emitters.In the example of FIG. 12, each such element or string 113 to 117comprises six of the 405 nm LEDs.

The electrical components shown in FIG. 12 also include a LED controlsystem 120. The control system 121 includes LED driver circuits for thevarious LEDs of the array 111 as well as a micro-control unit (MCU) 129.In the example, the MCU 129 controls the LED driver circuits viadigital-to-analog (D/A) converters. The driver circuit 121 drives theLEDs 113 of the first channel C1, the driver circuit 123 drives the LEDs115 of the second channel C2, and the driver circuit 125 drives the LEDs117 of the third channel C3. In a similar fashion, when active, thedriver circuit 127 provides electrical current to the other LEDs 119.

Although current modulation (e.g. pulse width modulation) or currentamplitude control could be used, this example uses constant current tothe LEDs. Hence, the intensity of the emitted light of a given near UVLED in the array 111 is proportional to the level of current supplied bythe respective driver circuit. The current output of each driver circuitis controlled by the higher level logic of the system, in this case, bythe programmable MCU 129 via the respective A/D converter.

The driver circuits supply electrical current at the respective levelsfor the individual sets of 405 nm LEDs 113-119 to cause the LEDs to emitlight. The MCU 129 controls the LED driver circuit 121 via a D/Aconverter 122, and the MCU 129 controls the LED driver circuit 123 via aD/A converter 124. Similarly, the MCU 129 controls the LED drivercircuit 125 via a D/A converter 126. The amount of the emitted light ofa given LED set is related to the level of current supplied by therespective driver circuit.

In a similar fashion, the MCU 129 controls the LED driver circuit 127via the D/A converter 128. When active, the driver circuit 127 provideselectrical current to the appropriate ones of the sleeper LEDs 119, forexample, one or more sleeper LEDs associated with a particular opticalelement/phosphor of the lighting device.

In operation, one of the D/A converters receives a command for aparticular level, from the MCU 129. In response, the converter generatesa corresponding analog control signal, which causes the associated LEDdriver circuit to generate a corresponding power level to drive theparticular string of LEDs. The LEDs of the string in turn output lightof a corresponding intensity to pump the phosphor in the associatedoptical element. The D/A converter will continue to output theparticular analog level, to set the LED intensity in accord with thelast command from the MCU 129, until the MCU 129 issues a new command tothe particular D/A converter.

The control circuit could modulate outputs of the LEDs by modulating therespective drive signals. In the example, the intensity of the emittedlight of a given LED is proportional to the level of current supplied bythe respective driver circuit. The current output of each driver circuitis controlled by the higher level logic of the system. In this digitalcontrol example, that logic is implemented by the programmable MCU 129,although those skilled in the art will recognize that the logic couldtake other forms, such as discrete logic components, an applicationspecific integrated circuit (ASIC), etc.

The LED driver circuits and the microcontroller 129 receive power from apower supply 1310, which is connected to an appropriate power source(not separately shown). For most general lighting applications, thepower source will be an AC line current source, however, someapplications may utilize DC power from a battery or the like. The powersupply 1310 provides AC to DC conversion if necessary, and converts thevoltage and current from the source to the levels needed by the LEDdriver circuits and the MCU 129.

A programmable microcontroller or microprocessor, such as the MCU 129,typically includes or has coupled thereto random-access memory (RAM) forstoring data and read-only memory (ROM) and/or electrically erasableread only memory (EEROM) for storing control programming and anypre-defined operational parameters, such as pre-established light datafor the current setting(s) for the strings of LEDs 113 to 119. Themicrocontroller 129 itself comprises registers and other components forimplementing a central processing unit (CPU) and possibly an associatedarithmetic logic unit. The CPU implements the program to process data inthe desired manner and thereby generates desired control outputs. Themicrocontroller 129 is programmed to control the LED driver circuits 121to 127 via the A/D converters 122 to 128 to set the individual outputintensities of the 405 nm LEDs to desired levels, and in this circuitexample to implement the spectral adjustment/control of the outputlight.

For example, the programming may define intensity levels or “recipes”for the strings of LEDs 113 to 119 to achieve preset combined coloroutputs produced by the pumped phosphors. The programming may also causethe MCU to vary respective intensity levels for the strings of LEDs 113to 119 to achieve particular variable color outputs over time, in apredefined sequence or cycle, for example, for a colored light showeffect.

The electrical system associated with the fixture also includes adigital data communication interface 139 that enables communications toand/or from a separate or remote transceiver (not shown in this drawing)which provides communications for an appropriate control element, e.g.for implementing a desired user interface. A number of fixtures of thetype shown may connect over a common communication link, so that onecontrol transceiver can provide instructions via interfaces 139 to theMCUs 129 in a number of such fixtures. The transceiver at the other endof the link (opposite the interface 139) provides communications to thefixture(s) in accord with the appropriate protocol. Different forms ofcommunication may be used to offer different links to the user interfacedevice. Some versions, for example, may implement an RF link to apersonal digital assistant by which the user could select intensity orbrightness settings. Various rotary switches and wired controls may beused, and other designs may implement various wired or wireless networkcommunications. Any desired medium and/or communications protocol may beutilized, and the data communication interface 139 may receive digitalintensity setting inputs and/or other control related information fromany type of user interface or master control unit.

To insure that the desired performance is maintained, the MCU 129 inthis implementation receives a feedback signal from one or more sensors143. A variety of different sensors may be used, alone or incombination, for different applications. In the example, the sensors 143include a light intensity sensor 145 and a temperature sensor 147. Acolor sensor may be provided, or the sensor 145 may be of a type thatsenses overall light intensity as well as intensity of light in variousbands related to different colors so that the MCU can determine color orspectral information from the measured intensities. The MCU 129 may usethe sensed temperature feedback in a variety of ways, e.g. to adjustoperating parameters if an excessive temperature is detected.

The light sensor 145 provides intensity information to the MCU 129. Avariety of different sensors are available, for use as the sensor 145.In a cavity optic such as in the device 50 of FIG. 8, the light sensor145 might be coupled to detect intensity of the integrated light eitheremitted through the aperture or as integrated within the cavity. Forexample, the sensor 145 may be mounted alongside the LEDs for directlyreceiving light processed within the optic. The MCU 129 uses the colorand/or intensity feedback information to determine when to activateparticular sleeper LEDs 119, e.g. to compensate for decreasedperformance of a respective set of LEDs for one of the initially activecontrol channels C1 to C3. The intensity feedback information may alsocause the MCU 129 to adjust the constant current levels applied to oneor more of the strings 113 to 117 of 405 nm LEDs in the control channelsC1 to C3, to provide some degree of compensation for decliningperformance before it becomes necessary to activate the sleepers.

Control of the near UV LED outputs could be controlled by selectivemodulation of the drive signals applied to the various LEDs. Forexample, the programming of the MCU 129 could cause the MCU to activatethe A/D converters and thus the LED drivers to implement pulse width orpulse amplitude modulation to establish desired output levels for theLEDs of the respective control channels C1 to C3. Alternatively, theprogramming of the MCU 129 could cause the MCU to activate the A/Dconverters and thus the LED drivers to adjust otherwise constant currentlevels of the LEDs of the respective control channels C1 to C3. However,in the example, the MCU 129 simply controls the light output levels byactivating the A/D converters to establish and maintain desiredmagnitudes for the current supplied by the respective driver circuit andthus the proportional intensity of the emitted light from each givenstring of LEDs. Proportional intensity of each respective string of LEDsprovides proportional pumping or excitation of the phosphors in opticalelements coupled to the respective strings and thus proportional amountsof phosphor light emissions in the output of the system.

For an ON-state of a string/channel, the program of the MCU 129 willcause the MCU to set the level of the current to the desired level for aparticular spectral or intensity setting for the system light output, byproviding an appropriate data input to the D/A converter for theparticular channel. The LED light output is proportional to the currentfrom the respective driver, as set through the D/A converter. The D/Aconverter will continue to output the particular analog level, to setthe current and thus the LED output intensity in accord with the lastcommand from the MCU 129, until the MCU 129 issues a new command to theparticular D/A converter. While ON, the current will remain relativelyconstant. The LEDs of the string thus output near UV light of acorresponding relatively constant intensity. Since there is nomodulation, it is expected that there will be little or no change forrelatively long periods of ON-time. However, the MCU can vary therelative intensities over time in accord with a program, to change thecolor tuning of the light output, e.g. in response to user input, over atiming cycle, based on time of day, or in response to a sensor thatdetects ambient light levels.

The discussion above has concentrated mainly on variable color lightingdevices or systems that may provide a wide range of possible types oflight output by using phosphors each having a substantially pure coloremission spectrum, for example. As the phosphor emission spectra becomemore pure, the spectra from the phosphor emissions effectively move outcloser to the edges of the CIE color chart, as illustrated in the CIEcharts for the simulations and the CIE chart for the specific RGBexample. The combined light output of a device or system using suchphosphors can generate visible output light within an operating gamuthaving vertices at the respective points corresponding to the phosphoremissions. Within that gamut, there may be some range of relativelywhite light and pastel colors, however, there will also be manydifferent highly saturated colors. Those skilled in the art willrecognize that the phosphor-centric light color control in devices andsystems that deploy phosphors remotely from the chips within the solidstate sources, for general lighting applications and similarapplications, may be used and implemented in a variety of different oradditional ways.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that the teachings may beapplied in numerous applications, only some of which have been describedherein. It is intended by the following claims to claim any and allapplications, modifications and variations that fall within the truescope of the present teachings.

What is claimed is:
 1. A solid state lighting device for variable colorlighting, comprising: a first solid state source configured to emitelectromagnetic energy in a predetermined spectrum; a first opticalelement arranged to receive electromagnetic energy from the first solidstate source; a first phosphor in the first optical element at alocation for excitation by the electromagnetic energy received from thefirst solid state source, the first phosphor being of a type excitableby electromagnetic energy of the predetermined spectrum and when excitedfor emitting visible light of a first color that is at leastsubstantially pure; a second solid state source configured to emitelectromagnetic energy in said predetermined spectrum; a second opticalelement arranged to receive electromagnetic energy from the second solidstate source but to receive little or no electromagnetic energy from thefirst solid state source, wherein the first optical element is arrangedto receive little or no electromagnetic energy from the second solidstate source; a second phosphor in the second optical element at alocation for excitation by the electromagnetic energy received from thesecond solid state source, the second phosphor being of a type excitableby electromagnetic energy of the predetermined spectrum and when excitedfor emitting visible light of a second color that is at leastsubstantially pure, the second color being different from the firstcolor, wherein: when the phosphors are excited, a visible light outputof the lighting device includes a combination of first and second colorlights emitted by the first and second phosphors, from the first andsecond optical elements, and color of the visible light output of thelighting device is adjustable in response to adjustment of respectiveintensities of the electromagnetic energy emitted by the first andsecond solid state sources to adjust relative levels of excitations ofthe first and second phosphors.
 2. The solid state lighting device ofclaim 1, wherein purity of each of the first and second color lightsemitted by the first and second phosphors is at least 0.8.
 3. The solidstate lighting device of claim 1, further comprising: a third solidstate source configured to emit electromagnetic energy in saidpredetermined spectrum; a third optical element arranged to receiveelectromagnetic energy from the third solid state source but to receivelittle or no electromagnetic energy from the first and second solidstate sources, wherein the first and second optical elements arearranged to receive little or no electromagnetic energy from the thirdsolid state source; a third phosphor in the third optical element at alocation for excitation by the electromagnetic energy received from thethird solid state source, the third phosphor being of a type excitableby electromagnetic energy of the predetermined spectrum and when excitedfor emitting visible light of a third color that is at leastsubstantially pure, the third color being different from the first andsecond colors, wherein: the visible light output of the lighting devicefurther includes light emitted by the third phosphor when excited, fromthe third optical element, in combination with the light emitted by thefirst and second phosphors when excited, from the first and secondoptical elements, and the color of the visible light output of thelighting device is further adjustable in response to adjustment ofrespective intensity of the electromagnetic energy emitted by the thirdsolid state source to adjust relative level of excitation of the thirdphosphor.
 4. The solid state lighting device of claim 3, wherein purityof the third color light emitted by the third phosphors is at least 0.7.5. The solid state lighting device of claim 3, wherein the adjustment ofthe levels of excitations of the first, second and third phosphorsenables adjustment of color of the combined light output over a widerange of different selectable colors encompassing much of the gamut ofvisible light.
 6. The solid state lighting device of claim 3, furthercomprising: a fourth solid state source configured to emitelectromagnetic energy in said predetermined spectrum; a fourth opticalelement arranged to receive electromagnetic energy from the fourth solidstate source but to receive little or no electromagnetic energy from thefirst, second and third solid state sources, wherein the first, secondand third optical elements are arranged to receive little or noelectromagnetic energy from the fourth solid state source; a fourthphosphor in the fourth optical element at a location for excitation bythe electromagnetic energy received from the fourth solid state source,the fourth phosphor being of a type excitable by electromagnetic energyof the predetermined spectrum and when excited for emitting visiblelight of a fourth color that is at least substantially pure, the fourthcolor being different from the first, second and third colors, wherein:the visible light output of the lighting device further includes lightemitted by the fourth phosphor when excited, from the fourth opticalelement, in combination with the light emitted by the first, second andthird phosphors when excited, from the first, second and third fourthoptical elements, and the color of the visible light output of thelighting device is further adjustable in response to adjustment ofrespective intensity of the electromagnetic energy emitted by the fourthsolid state source to adjust relative level of excitation of the fourthphosphor.
 7. The solid state lighting device of claim 6, wherein purityof the fourth color light emitted by the fourth phosphors is at least0.4.
 8. The solid state lighting device of claim 1, wherein each of thephosphors is a semiconductor nanophosphor.
 9. The solid state lightingdevice of claim 8, wherein each of the semiconductor nanophosphors is adoped semiconductor nanophosphor.
 10. The solid state lighting device ofclaim 1, wherein: the first optical element comprises a container havinga material bearing the first phosphor dispersed therein; the materialbearing the first phosphor dispersed therein appears at leastsubstantially clear when the first source is off; the second opticalelement comprises a container having a material bearing the secondphosphor dispersed therein; and the material bearing the second phosphordispersed therein appears at least substantially clear when the secondsource is off.
 11. The solid state lighting device of claim 10, whereinthe material bearing the first phosphor dispersed therein and thematerial bearing the second phosphor dispersed therein are solids. 12.The solid state lighting device of claim 10, wherein the materialbearing the first phosphor dispersed therein and the material bearingthe second phosphor dispersed therein are liquids.
 13. The solid statelighting device of claim 10, wherein: the container of the first opticalelement is formed of an optically transmissive material configured toact as a light guide with respect to electromagnetic energy receivedfrom the first source and to allow diffuse emissions of light emitted bythe first phosphor when excited; and the container of the second opticalelement is formed of an optically transmissive material configured toact as a light guide with respect to electromagnetic energy receivedfrom the second source and to allow diffuse emissions of light emittedby the second phosphor when excited.
 14. The solid state lighting deviceof claim 10, wherein the material bearing the first phosphor dispersedtherein and the material bearing the second phosphor dispersed thereinare gases.
 15. The solid state lighting device of claim 14, wherein eachof the gases comprises one gas or a combination of gases each selectedfrom the group consisting of: hydrogen gas, inert gases and hydrocarbonbased gases.
 16. The solid state lighting device of claim 1, wherein:each of the first and second solid state sources comprises one or morelight emitting diodes, each light emitting diode is rated for producingelectromagnetic energy of a wavelength in the range of 460 nm and below,and the absorption spectrum of each phosphor has an upper limit atapproximately 460 nm or below.
 17. The solid state lighting device ofclaim 1, further comprising: an optical mixing element optically coupledto the first and second optical elements to receive and mix lightemitted by the first and second phosphors when excited, from the firstand second optical elements, to form the visible light output of thesystem.
 18. The solid state lighting device of claim 17, wherein theoptical mixing element forms an optical integrating cavity.
 19. Thesolid state lighting device of claim 1, wherein the sources and theoptical elements are configured in a form factor of a lamp.
 20. Thesolid state lighting device of claim 19, wherein the form factor is aform factor of an incandescent lamp.
 21. The solid state lighting deviceof claim 19, wherein the form factor is a form factor of a tube lamp.22. The solid state lighting device of claim 21, wherein the form factorof the tube lamp is a form factor of a florescent tube lamp.
 23. Thesolid state lighting device of claim 1, wherein: the first opticalelement is configured to act as a light guide with respect toelectromagnetic energy received from the first source and to allowdiffuse emissions of light emitted by the first phosphor when excited;and second optical element is configured to act as a light guide withrespect to electromagnetic energy received from the second source and toallow diffuse emissions of light emitted by the second phosphor whenexcited.
 24. A lighting system comprising the solid state lightingdevice of claim 1 and a controller coupled to the first and second solidstate sources configured to implement independent control of the firstand second solid state sources.
 25. A solid state lighting device forvariable color lighting, comprising: a first optical element; a firstphosphor in the first optical element, the first phosphor being of atype excitable by electromagnetic energy of a first absorption spectrumand when excited for emitting visible light of a first color that is atleast substantially pure; a second optical element; a second phosphor inthe second optical element, the second phosphor being of a typeexcitable by electromagnetic energy of a second absorption spectrum andwhen excited for emitting visible light of a second color that is atleast substantially pure, wherein there is at least some overlap of thefirst absorption spectrum with the second absorption spectrum, the firstand second colors are different from each other, and a visible lightoutput of the lighting device includes a combination of the visiblelight of the first color emitted by the first phosphor when excited andthe visible light of the second color emitted by the second phosphorwhen excited; and first and second solid state sources for emittingelectromagnetic energy within the overlap of the first and secondabsorption spectra, wherein: the first solid state source and theoptical elements are arranged so that the first solid state sourcesupplies electromagnetic energy to excite the first phosphor in thefirst optical element but supplies little or no electromagnetic energyto excite the second phosphor in the second optical element, the secondsolid state source and the optical elements are arranged so that thesecond solid state source supplies electromagnetic energy to excite thesecond phosphor in the second optical element but supplies little or noelectromagnetic energy to excite the first phosphor in the first opticalelement, and the first and second solid state sources are independentlycontrollable to enable independent control of respective levelselectromagnetic energy for excitation of the first and second phosphorsto thereby independently control the relative levels of visible light ofthe first and second colors in the visible light output of the lightingdevice to achieve a desired color of the visible light output of thelighting device.
 26. The lighting device of claim 25, furthercomprising: a third optical element; a third phosphor in the thirdoptical element, the third phosphor being of a type excitable byelectromagnetic energy of a third absorption spectrum and when excitedfor emitting visible light of a third color that is at leastsubstantially pure, wherein there is at least some overlap of the first,second and third absorption spectra, the third color is different fromthe first and second colors, and the visible light output of the solidstate lighting device further includes the visible light of the thirdcolor emitted by the third phosphor when excited; and a third solidstate source for emitting electromagnetic energy within the overlap ofthe first, second and third absorption spectra, wherein: the third solidstate source and the optical elements are arranged so that the thirdsolid state source supplies electromagnetic energy to excite the thirdphosphor in the third optical element but supplies little or noelectromagnetic energy to excite the phosphors in the first and secondoptical elements, the first and second sources and the third opticalelement are arranged so that the third optical element receives littleor no electromagnetic energy to excite the third phosphor from the firstand second solid state sources, and the third solid state source iscontrollable independent of control of the first and second solid statesources to enable independent control of the respective level ofelectromagnetic energy for excitation of the third phosphor to therebyindependently control the relative level of visible light of the thirdcolor in the visible light output of the lighting device.
 27. The solidstate lighting device of claim 26, wherein the adjustment of the levelsof excitations of the first, second and third phosphors enablesadjustment of color of the combined light output over a wide range ofdifferent selectable colors encompassing much of the gamut of visiblelight.
 28. The lighting device of claim 26, further comprising: a fourthoptical element; a fourth phosphor in the fourth optical element, thefourth phosphor being of a type excitable by electromagnetic energy of afourth absorption spectrum and when excited for emitting visible lightof a fourth color that is at least substantially pure, wherein there isat least some overlap of the first, second, third and fourth absorptionspectra, the fourth color is different from the first, second and thirdcolors, and the visible light output of the solid state lighting devicefurther includes the visible light of the fourth color emitted by thefourth phosphor when excited; and a fourth solid state source foremitting electromagnetic energy within the overlap of the first, second,third and fourth absorption spectra, wherein: the fourth solid statesource and the optical elements are arranged so that the fourth solidstate source supplies electromagnetic energy to excite the fourthphosphor in the fourth optical element but supplies little or noelectromagnetic energy to excite the phosphors in the first, second andthird optical elements, the first, second and third sources and thefourth optical element are arranged so that the fourth optical elementreceives little or no electromagnetic energy to excite the fourthphosphor from the first, second and third solid state sources, and thefourth solid state source is controllable independent of control of thefirst, second and third solid state sources to enable independentcontrol of the respective level of electromagnetic energy for excitationof the fourth phosphor to thereby independently control the relativelevel of visible light of the fourth color in the visible light outputof the lighting device.
 29. The solid state lighting device of claim 25,wherein: the first optical element is configured to act as a light guidewith respect to electromagnetic energy received from the first sourceand to allow diffuse emissions of light emitted by the first phosphorwhen excited; and second optical element is configured to act as a lightguide with respect to electromagnetic energy received from the secondsource and to allow diffuse emissions of light emitted by the secondphosphor when excited.
 30. A lighting system comprising the solid statelighting device of claim 25 and a controller coupled to the first andsecond solid state sources configured to implement the independentcontrol of the first and second solid state sources.